Serum IGF-I levels were measured in 547 non-hypopituitaric, non-acromegalic healthy subjects of both sexes in Italy to develop reference values in relation to age and sex. Participant subjects were stratified in three age classes (25–39, 40–59 and ≥60 yr) and IGF-I assay was carried out by double-antibody radio immunoassay. Pearson’s correlation coefficient between age and IGF-I values was calculated by sex and predefined age ranges. IGF-I levels significantly decreased with age ( p <0.001, Kruskal-Wallis test) while sex was not a significant factor. The median IGF-I levels were 206 ng/ml in the 25–39 yr range, 147 ng/ml in the 40–59 yr range and 103 ng/ml in the ≥60 yr range. Pearson’s correlation coefficient confirmed the negative correlation between age and IGF-I levels in the total sample of subjects (r=−0.529). The r coefficient between age and IGF-I levels did not differ between sexes (r=−0.570 in males and r=−0.529 in females), thus reflecting no sex-effect on IGF-I levels decline over years. No correlations were found in the 25–39 yr range (r=−0.036) or in the 40–59 yr range (r=−0.080) either, while in subjects aged >60 yr, IGF-I levels tended to further decrease with increased age (r=0.389). Ranges of normal values set at the 2.5 th –97.5 th percentile in the three age ranges were 95.6–366.7 ng/ml between 25 and 39 yr, 60.8–297.7 ng/ml between 40 and 59 yr and 34.5–219.8 ng/ml in subjects aged ≥60 yr. This study may contribute to the development of age-specific reference ranges for IGF-I determination in serum of normal subjects of both sexes in Italy.

SummaryBackground The majority of patients with acromegaly have large tumours and the outcome of conventional management remains poor.Objective To investigate the clinical application of octreotide‐LAR as primary treatment in newly diagnosed patients with GH‐secreting pituitary tumours.Design Open, prospective, multicentre, 24‐week follow‐up study.Patients Thirty‐four patients were enrolled (20 men, 14 women; mean age, 50 years); 13 had microadenoma [median tumour volume 327 mm3 (range 31–629 mm3)], 21 had macroadenoma [median tumour volume 1325 mm3 (range 503–11583 mm3)].Interventions Octreotide‐LAR at the dosage of 20 mg every 28 days for the first 12 weeks increased to 30 mg every 28 days to control GH and/or IGF‐I excess in 20 patients (64·7%).Main outcome measures Primary endpoints were control of GH (fasting < 2·5 µg/l) and IGF‐I secretion (gender‐ and age‐normalized) and presence and entity of tumour mass shrinkage. Secondary endpoint was improvement of symptoms score.Results In patients with micro‐ and macroadenomas GH levels decreased to < 2·5 µg/l in 84·6% and 45%, serum IGF‐I levels normalized for age and gender in 61·5% and 35% of cases. Failure in achieving either GH < 2·5 µg/l or normal IGF‐I levels was found in none of the patients with micro‐ and in 45% of patients with macroadenoma. Median tumour volume was reduced by 54% (range: −90% to +350%) in micro‐ and by 49% (range −94% to −14%) in macroadenomas. Headache, perspiration and osteo‐arthralgias disappeared in 21%, paresthesias in 38%, fatigue in 26% and carpal tunnel syndrome in 15%. The treatment was well tolerated: more frequent adverse events were gastrointestinal (in 44%).Conclusions In both patients with micro‐ or macroadenoma, primary octreotide‐LAR treatment controls hormone excess, induces tumour shrinkage and improves symptoms of acromegaly with limited side effects and can be therefore successfully employed in patients with contraindications for surgery or in those who refuse surgery.

The aim of the present multicentric, open-label, non-comparative study was to evaluate the role of octreotide long-acting repeatable (LAR) as primary therapy for the treatment of GH-secreting pituitary macroadenomas. The patients received octreotide LAR 20 mg every 4 weeks for 12 weeks; afterwards the dose was confirmed or adjusted at 30 mg every 4 weeks, for the remaining 12 weeks, for responder or non-responder patients, respectively. Responder patients continued the study until 48 weeks. Twenty-one naïve active acromegalic patients were enrolled. In all patients, GH profile, IGF-I levels and magnetic resonance imaging (MRI) were evaluated at baseline and during treatment. The ability of octreotide LAR to decrease mean GH <2.5 μg/l and/or normalize IGF-I levels, adjusted for age and gender, was defined respectively as total or partial success. Total success was achieved in 5/21 (23.8%), 6/20 (30%) and 4/14 (28.6%) patients after 12, 24 and 48 weeks; partial success in 7/21 (33.3%), 9/20 (45%) and 9/14 (64%) patients at 12, 24 and 48 weeks according to GH levels, while according to IGF-I levels in 7/21 (33.3%), 7/20 (35%) and 5/14 (35.7%) patients at 12, 24 and 48 week. Tumor size was notably decreased after treatment with octreotide LAR: in 16 macroadenoma patients completing the study, the tumor sizes were 1609±1288, 818±616 (49.1±23.7%) and 688±567 mm 3 (54.6±24.4%) at baseline, 24 and 48 weeks. This study shows that oc-treotide LAR is effective in suppressing GH/IGF-I secretion and inducing tumor shrinkage in GH-secreting macroadenomas in a 48-week treatment. Octreotide LAR could be used as primary therapy in patients harbouring large pituitary tumors, who are less likely to be cured by neurosurgery.

Objectives: Growth Hormone (GH) promotes loss of body fat and causes insulin resistance. It is debated whether reduction of body fat mass during long term growth hormone (GH) administration improves carbohydrate metabolism. To answer this question we assessed carbohydrate handling and tissue specific function of the insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) during prolonged GH treatment of obese rats.Methods: Body fat % estimated by DEXA scanning, plasma IGF-I, glucose and insulin were studied ill 17 months old dietary induced obese rats treated for 4, 21 or 41 days (GH: 4 mg/kg/d or saline total n = 90). Adipose tissue, muscle and liver samples were obtained after 21 days and expression and tyrosine phosphorylation of IR and IRS-1 proteins and the degree of IRS-1-Jantis Kinase-2 (JAK2) interaction were analyzed by immunoprecipitation and immunoblotting.Resulls: Forty-one days GH treatment caused the body fat to decline significantly to 20 +/- 3% (Mean +/- SEM), whereas it remained steady on 51 +/- 4% in the pair fed group. Insulin levels in response to OGTT were significantly elevated throughout the experiment. IR amount was elevated in adipose tissue but decreased in liver after GH treatment while IR phosphorylation was increased in muscle only. IRS-1 amount was elevated in adipose tissue and muscle while IRS-1 phosphorylation was increased only in liver. The association of IRS-1 with JAK-2 was increased in liver and muscle.Conclusions: An extensive reduction of fat mass did not improved signs of insulin resistance in GH treated old obese rats. The molecular events associated with GH treatment included tissue specific changes in the function of IR and IRS-1 suggesting the liver to be the primary site of insulin resistance. Furthermore, the association of IRS-1with JAK-2 in the Course of GH signaling could present a mechanism for GH to directly induce insulin resistance. (C) 2004 Elsevier Ltd. All rights reserved.

Objectives Three major therapeutic modalities (transsphenoidal surgery, radiotherapy and medical therapy) are currently available for acromegaly. Although surgery is regarded as the primary option, 50-60% of macroadenomas require further treatment in the form of radiotherapy and/or medical therapy. Recent studies have suggested that radiotherapy might damage the normal hypothalamic-pituitary axis and also rarely leads to IGF-I normalization. The aims of this study were: (1) to examine the effect of different therapeutic modalities (transsphenoidal surgery, TSS; radiotherapy, RT; medical treatment with somatostatin analogues, SSA) on the daily spontaneous GH secretory pattern (day curve); and (2) to determine the relationship between the characteristics of the GH secretory pattern and the circulating concentration of IGF-I, acid-labile subunit (ALS) and IGFBP-3.Design and measurements Spontaneous GH secretion was evaluated at hourly intervals from 0800 to 1800 h. IGF-I, IGFBP-3 and ALS were measured in basal conditions. The mean and the minimum values obtained from the day curve profile and the coefficient of variation (CV) of single values, which are expressions of the magnitude of the spontaneous secretory pulses, were used for statistical analysis.Patients In a group of 45 acromegalic patients (28 women, mean age 51 years, range 26-83 years, and 17 men, mean age 57 years, range 37-78 years) treated with different protocols, including TSS, RT and SSA therapy, we evaluated GH secretion to determine the effect of single treatment options on the spontaneous secretory profile. Subjects were grouped on the basis of different therapeutic modalities: TSS + RT + SSA (group 1), TSS + SSA (group 2), SSA (group 3), TSS (group 4), TSS + RT (group 5). In patients treated with somatostatin analogues (SSA), tests were performed about midway between two injections.Results The number of deficiencies of the other pituitary functions (PD) was significantly higher in the groups that underwent RT (groups 1 and 5) than in the other groups; in both cases, P < 0.01. No significant differences were observed with regard to the mean GH, IGF-I, ALS or IGFBP-3 among the different treatment groups. A significant difference in the GH nadir was found between groups 2 and 4 (P = 0.042) and between groups 3 and 4 (P = 0.015). GH CV showed lower values in subjects who underwent RT (groups 1 and 5) than in the other groups. The difference was statistically significant between group 5 and groups 2, 3 and 4 (P < 0.05), between group 1 and groups 3 and 4 (P < 0.05), and between groups 2 and 4 (P = 0.007).Conclusions Our data confirm that radiation therapy decreases GH variability, and that this effect is probably due to hypothalamic damage, as already reported by others. In irradiated patients, a single random sample should therefore be sufficient to evaluate spontaneous GH secretion.

To study somatostatin/dopamine (SS/D) synergy in a human cell system constitutively expressing SS and D receptors (SSR and DR, respectively), we characterized the expression of SSR and DR subtypes in the non-small-cell lung cancer line Calu-6, and then we evaluated the effect on cell proliferation of SS/D chimeric molecules (BIM-23A387 and BIM-23A370), which bind with high affinity both sst(2) and D(2)R, and compared the results with those obtained by using SS-14 and subtype-selective SS analogs (SSA) and D agonists (DA). Because Calu-6 cells produce insulin-like growth factor (IGF) and IGF-binding protein (IGFBP) peptides, which play a role in the autocrine/paracrine control of cell growth, we also investigated the effects of chimeric compounds on secretion and expression of IGF system components. Relative high levels of sst(2) and the long isoform of the D(2)R were detected by real-time RT-PCR and Western blot in Calu-6, together with sst(5) and to a lesser extent sst(3) and D(4)R. BIM-23A387 and BIM-23A370 significantly inhibited growth of Calu-6, whereas IGF-IGFBP secretion or expression was unaffected, suggesting a direct inhibitory effect. The inhibition of cell growth, measured by both [(3)H]thymidine incorporation and cell count, was significantly lower when individual SSA and DA control peptides or subtype-specific SSA and DA were tested. BIM-23A370 was more potent than BIM-23A387 (P < 0.001). These findings show that SS/D chimeras can inhibit Calu-6 proliferation in an IGF-independent manner and suggest that this enhanced potency might be because of the induction of SSR/DR dimerization. The Calu-6 cell line, constitutively expressing SSR and DR, provides a suitable model to elucidate the mechanism of action of SSA and DA on regulation of cell growth and to characterize the interaction between SSR and DR.

The aim of our study was to evaluate the effect of α-interferon (α-IFN) on cell growth and on the different IGF system components in a human non-small cell lung cancer line (Calu-6) in vitro. Our results confirm the release of IGF-I and IGF-II by these cells. The amount of IGF-II in conditioned media (10.25±3.95 nM/106 cells, mean±SE) was more than 10-fold higher than that of IGF-I. α-IFN treatment reduced IGF-II levels in the media, with a maximal effect between 1 and 10 U/ml (Δ% of control: −31 and −55%, respectively, p<0.05). IGF-I was significantly reduced at 0.5 U/ml (p<0.01). No difference, however, was observed in IGF mRNA expression between untreated and α-IFN treated cells. An increase in IGF-I and IGF-II intracellular levels in α-IFN treated cultures was observed, suggesting that α-IFN can regulate the transfer of these peptides into the cells. Furthermore, IGF type-I and particularly type-II receptor expression was increased after α-IFN treatment. IGFBP-3 was detected only in trace amounts in the conditioned media; however, it showed an increase after α-IFN treatment (+110% at 1 U/ml). IGFBP-3 mRNA expression showed a slight increase after treatment with 1 and 10 U/ml. α-IFN (1-10 U/ml) reduced the stimulatory effect of IGF-I on cell replication (p<0.01), inhibited (p<0.01) cell replication in untreated and in fetal calf serum (FCS)-stimulated cells, and increased apoptosis in Calu-6 cells. Our data suggest that α-IFN may exert its effects at the cellular level in part through modification of the local IGF system.

Summaryobjective It has been suggested that the threshold of 1 µg/l of GH nadir after glucose load for definition of controlled acromegalic disease proposed in the 2000 consensus statement should be lowered to 0·30. We evaluated these two cut‐off values in comparison with IGF‐I, ALS and IGFBP‐3 in a group of acromegalic patients. With the aim of simplifying the follow‐up protocol in these patients we also tested if one single sample taken after glucose load could replace the nadir value.design and measurements GH secretion was evaluated by oral glucose tolerance test (OGTT), and by studying spontaneous secretion (GH day curve) with sampling at hourly intervals from 08·00 to 18·00 h; from the day curve, mean (MGHDC) and minimum (TRGH) values were considered. IGF‐I, ALS, and IGFBP‐3 were measured in the basal state at the first testing.patients Fifty acromegalic patients (26–83 years, 31 females, 19 males) in various phases of disease activity. Forty‐two patients had previously undergone pituitary surgery (10 also radiotherapy), 23 were treated with SMS analogues and three with dopamine agonist drugs.results The nadir GH value after glucose load correlated most significantly with the 120th‐minute sample (R = 0·95). Comparison of the postglucose 120th minute at the two cut‐off values with IGF‐I, IGFBP‐3 and ALS showed higher concordance of postglucose level at 0·3 with IGF‐I, while concordance was similar for the two cut‐off values with ALS and IGFBP‐3. When the 120th minute postglucose GH value is lower than 1 µg/l and IGF‐I is within 2SD for age nearly all other parameters are normal. IGF‐I correlated more with ALS (R = 0·78) than with IGFBP‐3 (R = 0·50) and the latter was less concordant with GH secretion parameters than the previous two.conclusions A sample taken at the 120th minute after glucose load, together with IGF‐I and/or ALS evaluation can give sufficient information for a routine assessment of disease activity, both in the diagnosis and in the follow‐up to treatment. If GH is lower than 1 µg/l and IGF‐I/ALS are normal, then the patient can be classified as ‘nonactive’ or ‘controlled’; a pathological IGF‐I and/or ALS value is a sign of disease activity irrespective of the GH values, while normal IGF‐I/ALS with an elevated GH requires further assessment.

Somatostatin and cortistatin, a recently discovered endogenous neuropeptide relative of somatostatin, have multiple modulatory effects on the immune system. The specific somatostatin receptor distribution might in part explain the heterogeneity of effects of somatostatin or its analogs on immunocytes. In fact, somatostatin receptor subtypes are differentially expressed on specific cell subsets within the organs of the immune system and the expression is dynamically regulated and seems to depend on the traffic of these cells through and within lymphoid structure and homing in tissues. Somatostatin effects on immune cells are mainly based on autocrine and paracrine modes of action. In fact, activated cells producing somatostatin (or cortistatin) may interact with other cells expressing the receptors. Here, we review the postulated modes of action of somatostatin and somatostatin-like peptides, including the currently available synthetic somatostatin analogs, in cells of the immune system. We also discuss the wide distribution of somatostatin and its specific five receptor subtypes in immune cell lines, as well as throughout animal and human lymphoid organs, in both normal and pathological conditions.

Dopamine is known to play a role in the modulation of aldosterone and catecholamine secretion from the adrenal gland, where dopamine receptors (DR), in particular the DR type 2 (D(2)), have been found to be expressed. DR expression has also been demonstrated in some types of benign adrenal tumors. The aims of the current study were to evaluate DR expression and D(2) localization in the normal adrenal gland and in different types of benign and malignant adrenal tumors, as well as to evaluate the in vitro effects of the dopamine agonists bromocriptine and cabergoline on hormone secretion in nontumoral adrenal cells. Adrenal tissues from 25 patients, subjected to adrenal surgery for different diseases, were studied. These included three normal adrenals; five adrenal hyperplasias; four aldosterone-secreting, two cortisol-secreting, and two clinically nonfunctioning adrenal adenomas; two aldosterone-secreting, two cortisol-secreting, and two androgen-secreting adrenal carcinomas; and three pheochromocytomas. In all tissues, DR and D(2) isoform (D(2long) and D(2short)) expression was evaluated by RT-PCR. D(2) localization was also evaluated by immunohistochemistry using a specific polyclonal antibody, whereas D(2)-like receptor expression was evaluated by receptor-ligand binding study, using the radiolabeled D(2) analog (125)I-epidepride. The effects of bromocriptine and cabergoline on baseline and ACTH and/or angiotensin II-stimulated aldosterone, cortisol, and androstenedione secretion were evaluated in cell cultures derived from five different adrenal hyperplasia. At RT-PCR, both D(1)-like and D(2)-like receptors were expressed in all normal and hyperplastic adrenals. D(2) and D(4) were expressed in aldosterone- and cortisol-secreting adenomas, cortisol-secreting carcinomas, and clinically nonfunctioning adenomas, whereas no DR was expressed in aldosterone- and androgen-secreting carcinomas. D(2), D(4), and D(5) were expressed in pheochromocytomas. In all D(2)-positive tissues, both D(2) isoforms were expressed, with the exception of one case of aldosterone-secreting adenoma and the cortisol-secreting carcinomas, in which only the D(2long) isoform was expressed. D(2)-like receptor expression was confirmed at receptor-ligand binding study. At immunohistochemistry, D(2) was mainly localized in the zona glomerulosa and reticularis of the adrenal cortex and, to a lesser extent, in the zona fasciculata and medulla of normal and hyperplastic adrenal tissue. In the positive tumors, D(2) was localized in the tumoral cells. At the in vitro study, a significant inhibition of both baseline and ACTH-stimulated aldosterone secretion was found after high-dose cabergoline, but not bromocriptine, administration; and a significant inhibition of angiotensin-II-stimulated aldosterone secretion was found after both bromocriptine and cabergoline administration in the adrenal hyperplasias. In conclusion, the current study demonstrated that both D(1)-like and D(2)-like receptors are expressed in the normal adrenal gland and in a percentage of adrenal adenomas or carcinomas. Bromocriptine and cabergoline induce only a minor inhibition of the secretion of adrenal hormones in the nontumoral adrenal gland in vitro, not excluding, however, the possible effective use of dopamine agonists in vivo in the treatment of adrenal tumors.

Acromegaly is a rare and chronic disease that, in the majority of cases, is due to the presence of a benign growth hormone (GH)-producing tumor of the pituitary. In the past, the diagnosis of acromegaly was established basically on physical changes, and only the patients with a severe clinical picture were brought to medical attention. The development of a radioimmunoassay for detecting GH allowed for the first time to confirm the diagnosis biochemically. Subsequently, methods for measuring insulin-like growth factor 1 (IGF-I) became available and added another important biochemical marker for the diagnosis and follow-up of these patients. Progressive improvements in assay methods have allowed for progressively better definitions of normality and, as a result, have permitted the diagnosis to be biochemically established in patients with only mild forms of the disease. Moreover, new potential markers of disease activity, such as other GH-dependent IGF system parameters, have been investigated and proposed in the diagnostic work-up and for monitoring the therapeutic outcome. Optimal assessment of disease activity, for both diagnostic and follow-up purposes, is mandatory. This subject has been strongly debated regarding proper cut-off values using highly sensitive GH assays as well as the problems linked to IGF system components measurement. Consequently, several consensus reports, as well as original studies, have been issued giving special attention to diagnostic procedures, cut-off revisions and definition of disease activity. The present review discuss principally the biochemical diagnosis of acromegaly based on these articles and on the experience collected in an endocrinological unit considered as reference center for pituitary diseases.

Besides anabolic steroids, the most common performance-enhancing hormones are erythropoietin (EPO), insulin, GH, and gonadotropins, mostly indistinguishable from endogenous hormones and with very short half-life. This makes virtually impossible to demonstrate their use by measuring their concentration in the blood or urine. A possible approach to the problem may lie in indirect demonstration through detection of the biological effects of these substances.

The insulin-like growth factor (IGF) system plays an important role in the autocrine and paracrine regulation of bone formation and remodeling. The aim of this study was to evaluate the role of the autocrine IGF system during osteogenic differentiation in rat tibial osteoblasts (ROB) in culture. In this in vitro model, the stages of osteogenesis studied were S1, corresponding to the onset of alkaline phosphatase (AP) expression (days 0-3); S2, coincident with the peak of AP expression in differentiation culture conditions (days 4-6), and S3, corresponding to the onset of mineral deposition in the extracellular matrix (days 7-9). The results showed that conditioned medium of ROB contains greater amounts of IGF-II than IGF-I at all differentiation stages. Both peptides showed the highest concentrations on day 3 of differentiation (end of S1). All IGF-binding proteins (IGFBPs), except IGFBP-1 and -6, were detected, and IGFBP-2 was the most abundant IGFBP present in the conditioned media, and its degradation increased from S1 to S3. By semiquantitative RT-PCR, IGF-I and IGF-II were highly expressed on days 3 and 6, whereas IGFBP-2 was constantly expressed. We focused our study on the role of IGF-II and IGFBP-2 on the synthesis of AP, an early marker of osteoblast maturation. The results showed that a significant increase in AP expression was induced by IGF-II added to the differentiating osteoblasts continuously or in S1 but not in S2 or S3. IGFBP-2 was able to potentiate endogenous and exogenous IGF-II-dependent stimulation of AP activity, and its proteolytic degradation in late stages of osteogenesis (S2 and S3) was highly correlated with the increase of active matrix metalloproteinase-2 in the CM and with the decreased efficacy of IGF-II action. These data suggest that IGFBP-2, at nearly equimolar concentration with IGF-II, plays a potentiating role in IGF-II action on ROB differentiation in vitro.

The height of subjects with constitutionally tall stature (CTS) is at least 2 SD above the mean of subjects of the same age and sex. Apart from a few discordant data on the role of GH and its direct mediator, IGF-I, no studies have been conducted on other components of the IGF system, which also condition the bioavailability and activity of IGF-I. We, therefore, investigated the possibility that other components of the IGF system might play a role in determining the increased growth velocity seen in CTS. To this end, we evaluated the behavior not only of IGF-I but also of IGF-II, IGF-binding protein (IGFBP)-3, and acid-labile subunit, the subunits that constitute the main IGF complex in circulation (150-kDa complex), as well as of IGFBP-1 and IGFBP-2, which are negatively regulated by GH and, like IGFBP-3, able to influence the bioavailability of the IGFs. The study was performed on 22 prepubertal subjects affected by CTS (16 males and 6 females), aged 2.8-13.3 yr (6.8 +/- 0.5 yr, mean +/- SEM). Thirty-seven normal prepubertal subjects (16 males and 21 females) aged between 2.2 and 13.3 yr (6.7 +/- 0.5 yr), who were comparable in socioeconomic and nutritional terms, served as controls. From the auxological point of view, subjects with CTS differed significantly from controls only in terms of growth velocity (HV-SD score; CTS, 1.8 +/- 0.3; controls, 0.4 +/- 0.2; P < 0.0001) and height (H-SD score; CTS, 3.1 +/- 0.1; controls, 0.4 +/- 0.2; P < 0.0001). The results demonstrated that the concentrations of IGF-I (27.3 +/- 2.0 nmol/liter), IGFBP-3 (66.9 +/- 3.8), and acid-labile subunit (216.8 +/- 13.6) in CTS-affected subjects were not significantly different from those determined in controls (25.0 +/- 2.9, 74.4 +/- 4.1, and 241.0 +/- 11.9, respectively). By contrast, IGF-II levels proved significantly higher in CTS subjects (IGF-II: 87.2 +/- 3.4 vs. 52.4 +/- 2.3, P < 0.0001). Chromatographic analysis, performed after acid treatment of pooled sera, showed only the presence of normal 7.5-kDa IGF-II in both CTS subjects and controls. In comparison with controls, CTS children showed a lower concentration of IGFBP-1 (1.6 +/- 0.3 vs. 4.1 +/- 0.7, P = 0.03) and a higher concentration of IGFBP-2 (14.3 +/- 1.8 vs. 9.6 +/- 1.1, P = 0.03). The IGFs (IGF-I and -II)/IGFBPs (-1 + -2 + -3) molar ratio was significantly higher (P < 0.0001) in CTS children than in controls. In particular, the IGF-II/IGFBP ratio (P < 0.0001) was responsible for the excess of the IGF peptide in relation to the concentrations of IGFBPs and, therefore, for the increase in the potentially bioactive free form of the IGFs. Moreover, the IGFBP-3/IGF molar ratio was significantly reduced, being less than 1 in CTS subjects (0.6 +/- 0.1 vs. 1.1 +/- 0.1), so that a quantity of IGF peptides lack sufficient IGFBP-3 to form the 150-kDa complex with which are normally sequestered in the vascular compartment. The data show that in CTS: 1) the most GH-dependent components of the IGF system are normal, consistent with the finding of a normal GH secretory state; 2) the less GH-dependent IGF-II is significantly increased, in agreement with the finding of a relationship between high levels of IGF-II and overgrowth in some syndromes; and 3) the IGF/IGFBP molar ratio is increased, and, therefore, a greater availability of free IGF for target tissues may be responsible for overgrowth in CTS.

In normal subjects the main form of circulating insulin-like growth factor (IGF) is the 150-kDa complex. This complex is formed by the IGF peptide, the acid-stable IGF-binding protein-3 (IGFBP-3), and the acid-labile subunit (ALS). Experimental and clinical data have demonstrated that ALS is primarily under the control of GH and plays a critical role in maintaining constant levels of circulating IGF-I. In this study we evaluated ALS, IGF-I, and IGFBP-1, -2, and -3 in 45 acromegalic patients in basal conditions and, in 37 of these, twice after surgical therapy compared with 100 age- and sex-matched control subjects to estimate their value as parameter of GH secretory state. The results demonstrated that in acromegaly before treatment all parameters (ALS, 523 +/- 26; IGF-I, 129 +/- 6; IGFBP-1, 0.7 +/- 0.1; IGFBP-3, 234 +/- 21; nmol/L; mean +/- SEM) but IGFBP-2 were significantly different (P<0.0001) from those in healthy subjects (ALS, 281 +/- 4; IGF-I, 22 +/- 1; IGFBP-1, 1.6 +/- 0.1; IGFBP-3, 91 +/- 3). IGF-I was more sensitive (100%) than ALS (89%), and both were more predictive of disease status than IGFBP-3, in that 27% of the patients had IGFBP-3 levels within the normal range. Considering the ALS/IGFBP-3 molar ratio, almost 55% of ALS circulated in a free form in active acromegaly. Before treatment, the IGF-I/IGFBPs (-1 + -2 + -3) molar ratio, which can be regarded as free, biologically active, IGF-I, was greatly increased (0.77 +/- 0.06; P<0.0001) compared with that in control subjects (0.23 +/- 0.01). After surgery, all 10 patients with controlled disease showed normalization of ALS (100% sensitivity), whereas 9 of them had normal IGFBP-3; reevaluation after varying lengths of time showed all these parameters within the normal range. In the 27 patients with active disease, IGF-I and ALS were more predictive of disease status (91% and 83% negative predictive values, respectively) than IGFBP-3 (53%). The basal ALS concentration correlated only with IGFBP-3 (r = 0.70; P<0.001). In postsurgery samples (first control) a statistically significant (P<0.001) correlation was found between mean GH values as well as minimum GH after oral glucose tolerance test and ALS (r = 0.72 and 0.83, respectively), IGF-I (r = 0.69 and 0.77), IGFBP-3 (r = 0.50 and 0.72), and IGFBP-2 (r = -0.36 and -0.63). Similarly, IGF-I, IGFBP-3, and ALS were positively correlated among themselves and negatively correlated with IGFBP-2 (P<0.001). In conclusion, in the diagnosis of acromegaly, the measurement of total IGF-I appears to be the most sensitive parameter among the subunits of the 150K complex, and IGFBP-3 the least sensitive. For ALS, this subunit is quite sensitive and appears to be a useful parameter in reassessment after surgical treatment.

Insulin‐like growth factor‐I (IGF‐I) promotes proliferation, differentiation and survival of Schwann cells (SC). Moreover, an effect of IGF‐I on axon regeneration has been proposed. However, although IGF‐I expression has been shown in postnatal SC and in SC precursors thus suggesting an autocrine regulation of SC survival, release of the trophic factor by SC has not been clearly demonstrated. To investigate the role of the IGF system, we studied the supernatant of primary SC cultures, purified sensory neuron cultures, and co‐cultures of SC and sensory neurons. Moreover, since in its free form IGF‐I interacts with specific binding proteins (IGFBPs) whose active role in modulating the effects of IGF‐I is increasingly recognized, in the same culture systems we also evaluated levels of IGFBP‐1 and ‐3. We established SC, sensory neuron and SC/sensory neuron cultures according to classical procedures. Purified SC (87,500 cells/dish) were grown in presence of serum, forskolin, cholera toxin and bovine pituitary extract. Purified sensory neurons were grown in the presence of serum and NGF; part of it was maintained alone and the rest was added with SC (87,500 cells/dish) and grown in a co‐culture system. After 1 month all cultures were washed with PBS and grown for at least 4 days in a serum‐free medium before collecting their conditioned media (CM) for chromatography assays. Similar IGF‐I levels were found into the CM of SC and of sensory neurons when grown as purified cultures (94.40 vs 73.80 ng/5×106 cell). Instead, higher amounts of IGF‐I were detected into the medium of SC/sensory neurons co‐cultures (277.70 ng/5×106 cell). IGFBP‐1 and ‐3 production was also found in both SC and sensory neuron purified cultures, but their expression was clearly higher in neurons compared to SC (0.74 vs 0.28 ng/5×106 cell for IGFBP‐1 and 4.48 vs 1.77 ng/5×106 cell for IGFBP‐3). Furthermore, SC/sensory neuron co‐cultures maintained high levels of IGFBP‐3 (3.93 ng/5×106) but not of IGFBP‐1 (0.28 ng/5×106). In conclusion, IGF‐1 is produced by both SC and pure sensory neurons, but co‐culturing the two cell populations results in a possible reciprocal stimulation to synthesize this growth factor. Moreover, the decrease of IGFBP‐1 in the medium of co‐cultures could be due to the production of IGFBP proteases by SC. This action could be a mechanism to increase IGF‐1 availability to the specific receptor.

High insulin-like growth factor-I (IGF-I) levels are associated with an increased risk of breast cancer in premenopausal women. Because the synthetic retinoid fenretinide showed a beneficial effect on second breast cancers in premenopausal women in a Phase III trial, we studied its long-term effects on IGF-I levels. We measured, at yearly intervals for up to 5 years, the circulating levels of IGF-I, IGF binding protein (BP)-3, and their molar ratio in 60 subjects < or = 50 years of age and 60 subjects > 50 years of age allocated either to fenretinide or no treatment. In women < or = 50 years of age, measurements of IGF-II, IGFBP-1, and IGFBP-2 were also performed. The associations between biomarkers and drug or metabolite plasma concentrations were also investigated. All biomarkers were relatively stable over 5 years in the control group. Compared with controls and after adjustment for baseline, treatment with fenretinide for 1 year induced the following changes: IGF-I, -13% [95% confidence interval (CI), -25 to 1%] in women < or = 50 years of age and -3% (95% CI, -16 to 13%) in women > 50 years of age; IGFBP-3, -4% (95% CI, -12 to 6%) in both age groups; IGF-I:IGFBP-3 molar ratio, -11% (95% CI, -22 to 1%) in women < or = 50 years of age and 1% (95% CI, -11 to 16%) in women > 50 years of age. These effects were apparently maintained for up to 5 years, although fewer samples were available as time progressed. No change in other IGF components was observed. Drug and metabolite concentrations were negatively correlated with IGF-I and IGF-I:IGFBP-3 molar ratio in women < or = 50 years of age. Fenretinide induces a moderate decline of IGF-I levels in women < or = 50 years of age. The association between IGF-I change and the reduction of second breast cancers in premenopausal women warrants further study.