Journal Article MATURATION OF GONADOTROPHIN REGULATION IN ADOLESCENT GIRLS Get access Th Lemarchand-Béraud, Th Lemarchand-Béraud Division de Biochimie Clinique, Département de Médecine et de Gynéccl C.H.U.V., 1011 Lausanne, Switzerland Search for other works by this author on: Oxford Academic Google Scholar M Reymond, M Reymond Division de Biochimie Clinique, Département de Médecine et de Gynéccl C.H.U.V., 1011 Lausanne, Switzerland Search for other works by this author on: Oxford Academic Google Scholar G Magrini, G Magrini Division de Biochimie Clinique, Département de Médecine et de Gynéccl C.H.U.V., 1011 Lausanne, Switzerland Search for other works by this author on: Oxford Academic Google Scholar M Zufferey, M Zufferey Division de Biochimie Clinique, Département de Médecine et de Gynéccl C.H.U.V., 1011 Lausanne, Switzerland Search for other works by this author on: Oxford Academic Google Scholar I Rey I Rey Division de Biochimie Clinique, Département de Médecine et de Gynéccl C.H.U.V., 1011 Lausanne, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Acta Endocrinologica (Norway), Volume 92, Issue 2_Supplement_b, Aug 1979, Pages S354–S358, https://doi.org/10.1530/acta.0.091S354 Published: 01 August 1979

Puberty is characterized by a progressive maturation of the hypothalamus-pituitary gonadal axis which, in girls results in menarche. The first menstrual cycles are usually irregular and anovulatory, and the subtle positive and negative regulation of sex steroids on the hypothalamus-pituitary axis has probably not reached adult maturity. An investigation has been carried out in 99 normal adolescent girls, divided into 3 groups: 1-2, 3-4 and 5 years after menarche, by measuring basal hormonal values as well as the responses to LHRH and TRH during the follicular and luteal phases. Basal FSH and LH values reached adult levels after the second year of menarche, while FSH and LH responses to 50microgram LHRH showed a regular and progressive increase from 1 to 5 years post-menarche, resulting, in the 5-year group and in spite of the half dose received, in definitely higher FSH and LH responses than those observed in the adult women after 100 microgram LHRH. This enhanced pituitary responsiveness to LHRH is due to still progressively increasing estradiol and progesterone secretions, the latter hormone remaining still lower than in the adults. Basal prolactin levels were significantly higher than those found in adult women with a slightly increased prolactin response to TRH and an exaggerated one of TSH, with normal T3 and T4 levels. These data show that from the onset of menarche to the complex and subtle adult menstrual cycle regulation, there is a continuing maturation of the hypothalamus-pituitary axis of the gonads which lasts approximately 5 years. It is characterized by increasing E2 secretion, low progesterone secretion and slightly increased prolactin levels, with a frequently impaired luteal phase. The enhanced pituitary sensitivity to releasing hormones is due to the positive feedback mechanism of E2 which is not yet associated with adequate progesterone secretion for a negative feedback, as in adult women. Thus, adolescence is still a maturation period, the onset of ovulation being the final step in this development.

The effect of exogenous sex steroid hormones taken as contraceptives was studied in 15 women. Significantly lower luteinizing hormone (LH) and follicle stimulating hormone (FSH) basal values as well as responses to LH releasing hormone (LH-RH) were observed in 8 normal women under combination oral contraceptives. Conversely in 7 women taking sequential oral contraceptives basal LH and FSH remained within the normal range. The LH-FSH responses were increased and delayed when the tests were performed during the period of estrogen treatment. Thus with combination oral contraceptives constant high levels of estrogens and progesterone inhibit the LH peak and also decrease the basal LH-FSH levels and responses to the releasing hormone while with sequential drugs the low level of estradiol does not inhibit such responses and even enhances them. In menopausal women both basal and gonadotropin responses to LH-RH were increased indicating a considerable pituitary reserve. In menstruating women a significant estradiol increase is observed 2 and 4 hours after a 100 mcg injection of LH-RH both during the follicular and the luteal phases whereas progesterone increases only in the luteal phase. In men testosterone was found to increase 4 hours after a 100 mcg injection of LH-RH. The findings show that in normal subjects sex steroid hormones are important regulators of the sensitivity of the pituitary response to the releasing hormone.(Authors modified)

In man both basal gonadotrophin levels and the pituitary responses to LHRH remained relatively constant throughout life. In women the pituitary sensitivity varied in the menstrual cycle due to the typical cyclic variation of oestradiol and progesterone. The max delta LH increase to 100 mug LHRH was observed in the periovulatory period (183 +/- 41 mU/ml); it was also significantly higher in the luteal (49 +/- 7 mu/ml) than in the early follicular phase (18 +/- 3 mU/ml). The effect of exogenous sex steroid hormones taken as contraceptive drugs was then studied in 15 women. Significantly lower LH and FSH basal values as well as responses to LHRH were observed in 8 normal women under oral combined contraceptives. Conversely, in 7 women under oral sequential contraceptives, basal LH and FSH remained in the normal range. The LH-FSH responses were increased and delayed when these tests were performed during the period of estrogen treatment. Thus, with combined oral contraceptives, constant and high levels of estrogens and progesterone not only inhibit the LH peak, but also decrease the basal LH-FSH levels and responses to releasing hormone. Conversely, with sequential oral contraceptives, the low level of estradiol does not inhibit these responses and even enhances them. In menopausal women both basal and gonadotrophin responses to LHRH were increased indicating an important pituitary reserve. In menstruating women a significant estradiol increase is observed 2 and 4 hours after a 100 mug LHRH injection, both during the follicular and the luteal phases whereas progesterone increases only in the luteal phase. In men, testosterone was found to increase 4 hours after a 100 mug LHRH injection. These studies show that in normal subjects, sex steroid hormones are important regulators of the sensitivity of the pituitary responsiveness to releasing hormone.