Serum follicle-stimulating hormone levels in puberty

Serum follicle-stimulating hormone levels in puberty

Serum follicle-stimulating hormone levels in puberty S. S. W. J. Cleveland, C. YEN* VICIC”” Ohio The present study was designed to determine...

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Serum follicle-stimulating

hormone levels

in puberty S.

S.

W.

J.

Cleveland,

C.

YEN*

VICIC”” Ohio

The present study was designed to determine the chronological changes in the concentration of immunoreactive FSH in serum during the period of sexual maturity. Serum FSH concentrations were determined by a specific radioimmunoassay in 174 school boys and girls from 8 through 14 years of age and in adult males and females. The data show that there was a progressive rise in serum FSH concentration with advancing age which reached a plateau by age 14 for both boys and girls. At that time the FSH concentration doubled, nearing the adult values for both sexes. Girls have significantly higher FSH concentration than boys at corresponding ages of 10, 11, and 12. A significant rise of FSH occurred between ages 9 and 10 in girls and between ages II and 12 in boys. Thus FSH secretion in boys lags chronologically behind girls by about I to 2 years. In girls, menarche was associated with a rapid rise in LH without any significant change in FSH.

sistently higher concentrations of LH were observed in girls than in boys between 8 through 14 years of age. In the current study, the serum FSH concentrations were determined by specific radioimmunoassay in the sera of the same groups of boys and girls. Correlation was made between serum FSH concentration and the menarche in girls.

of radioimmuwhich are capable of noassay techniques measuring small amounts of follicle-stimulating hormone (FSH) in serum1 has made it possible to quantitate the serum FSH concentration in children. Recently, we have reported2 that luteinizing hormone (LH) as determined by radioimmunoassay showed a progressive increase in serum concentration as sexual maturity was reached. However, there appears to be a difference in the LH increments between boys and girls; conTHE

INTRODUCTION

From the Department Biology, Case-Western School of Medicine.

Material

methods

For this study, as for the LH studies reported previously,’ 174 Caucasian children between ages 8 and 14 were selected randomly from local schools. The children were not examined by us but had had physical examinations within a year of the study and were considered healthy. Of these children, 82 were girls and 92 were boys. Their age distributions are shown in Fig. 1. The age groups were assigned according to the last birthday. Among the girls, the age of menarche was recorded. Seventeen of the 43 girls in the 11, 12, 13 year age groups, and all 11 girls in the age 14 group were postmenarchial. In each illstance the nature of the investigation was

of Reproductive

Reserve

and

University

This study was supported in part by grants from the American Cancer Society <(T-504) and the Pardee Foundation. Presented in part at the Fifty-first @docrine Society Annual Meeting yg6Ngew York, New York, June 27, “Address reprint requests to S. S. C. Yen, Department of Reproductive Biology, MacDonald House, University Hospitals, Cleveland, Ohio 44106. **Third-year medical student; the work done was in partial fulfilment of the requirements for the degree of Doctor of Medicine. 134

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106 1

Serum

explained to the parents and the child and their consent was obtained. Venous blood samples were obtained between the hours of 1:OO and 4:00 P.M. Serum was separated immediately and stored at -20’ C. until assayed. The double-antibody radioimmunoassay for serum FSH used in this study was similar to that described by Midg1ey.l Purified human pituitary FSH (LER 780) * was used for iodination and rabbit anti-FSH serum (absorbed with HCG) * was used as first antibody. The Second International Reference Preparation of Human Menopausal Gonadotropin (2nd IRP-HMG) + was used as a standard. The values were expressed as milli-International Units per milliliter of serum in terms of 2nd IRP-HMG. The lower limit of sensitivity of the assay was between 1.5 and 3.0 m1.U. per milliliter. All samples from the 174 children were determined in the same assay in duplicate to eliminate interassay error. Serum FSH levels from 12 eugonadal adult males and 12 adult females were determined and the mean values used for comparison. All the statistical calculations of the data were analyzed by the programmed computer for the mean + S.E. and the p values (Student’s t test). Results The results of the serum FSH concentrations are analyzed in accordance with their age and sex. The individual values from each subject are plotted in Fig. 1 and the mean concentrations (f SE.) for boys and girls as well as for the adult subjects are shown in Fig. 2. As can be seen, FSH is detectable in the serum at 8 years of age in both boys (3.15 + 0.17 m1.U. per milliliter) and girls (4.4 t 0.32 m1.U. per milliliter). There is a progressive rise in serum FSH concentration with advancing age, reaching a plateau by age 14 for both boys and girls. There is approximately a twofold increase in FSH concentration from age 8 to age 14 *Purified FSH (LER 780) prepared by Dr. Leo Reichert and anti-FSH serum (No. 510, absorbed with HCG) prepared by Dr. A. R. Midgley, Jr., were gifts from Dr. A. R Midgley. for

+Znd IRP-HMG, Medical Research,

distributed Mill Hill,

by the London,

National Institute N. W. 7, England.

FSH

levels

in puberty

135

15.

FSH mIu/mI

IO-

5-

I: FSH I(

mIu/ml

AGE

GROUPS

Fig. 1. The individual values of serum FSH concentration from each subject are plotted according to their age for boys and girls. The adult male and female values are also plotted for the purpose of comparison.

20$ 3 z i.5 L

MEAN+SE 3 BOYS IGIRLS

15IO5-

B

9 IO 11 I2 13 14 ADULT AGE GROUPS Fig. 2. The mean (t S.E.) serum FSH concentration in age groups. Adult values are also shown for the purpose of comparison.

136

Yen

and

Vicic

Amer.

for boys (from 3.15 + 0.17 to 8.77 + 0.49 m1.U. per milliliter) and for girls (from 4.4 t 0.32 to 9.28 + 0.88 m1.U. per milliliter). The pattern of FSH secretion in boys and girls during pubescence appeared qualitatively and quantitatively different; significantly higher concentrations of FSH were observed in girls than in boys at ages 10 (p < 0.05)) 11 (p < O.Ol), and 12 (p < 0.05). Thereafter, the mean serum FSH concentrations were comparable and have essentially reached the values for the adult male (9.1 ri: 0.5 m1.U. per milliliter) and adult female (12.2 t 0.6 m1.U. per milliliter). I n girls, a significant rise in serum FSH concentration occurred between ages 9 and 10 (4.36 i 0.3 versus 8.11 t 1.4 m1.U. per milliliter, p < 0.05). In boys, a significant rise occurred between ages 11 and 12 (5.92 i 0.28 versus 8.40 + 0.8 m1.U. per milliliter, p < 0.05). When the serum FSH concentration was compared in premenarchial and postmenarchial girls of the same age, it was found that the serum FSH concentration was almost identical (Fig. 3). The LH concentration, on the other hand, was significantly higher in postmenarchial girls than in premenarchial girls (p < 0.05) . Comment Since puberty occurs between

(sexual maturity) generally ages 10 and 12 in girls and

PRE. (26)

POST (17)

Fig. 3. The mean (i: S.E.) serum FSH (solid line) and serum LH (broken line) concentrations for 26 premenarchial girls and 17 postmenarchial girls of the same age group (ages 11, 12, and 13). The age 14 group is not included for the comparison since all 11 girls in this age group are postmenarchial.

January J. Obstet.

1, 1970 Gynec.

ages 11 and 13 in boys,3 we have selected the age groups of 8 through 14 in an attempt to determine the chronological changes in the FSH secretion during puberty. The present study demonstrates that the immunoreactive FSH, like that of the imrnunoreactive LH,’ is detectable in serum at 8 years of age for both sexes. Others using radioimmunoassay have reported that the serum FSH is detectable in children less than 8 years of age.4B 5 The serum FSH rises progressively with advancing age and reaches a plateau at the age of 14 with a mean concentration which is comparable to the adult values for both sexes. There was a twofold increase in FSH concentration during the period of sexual maturity for both boys and girls, but FSH secretion in boys lags chronologically behind girls by about 1 to 2 years (Fi?. 2). As we have previously shown in the same groups of children, there is a sixfold increase in mean LH concentration in girls between 8 and 14 years of age and only threefold increase in boys.” These data are consistent with the fact that the onset of puberty is later in the boys than in the girls.3 It should be noted that several values observed in the boys ages 8 and 9 were at the lower limit of sensitivity of the assay (Fig. 1). Thus, the mean values in these two age groups may not be entirely representative. Using radioimmunoassay, Schalch, Bryson, and Lee4 have reported a gradual but significant rise of FSH prior to adolescence. Raiti and associates5 have shown a rise in FSH in boys between ages 9 to 11 years and correlated this rise in FSH with early stages of pubertal development. However, there are no comparable published data with which to compare our serum FSH levels in girls. The mean FSH levels for the adult female (12.5 + 0.6 m1.U. per milliliter) and for the adult male (9.1 + 0.5 mI.U. per milliliter) are comparable to those reported by others.63 7 Previous studies on the excretion of total urinary gonadotropins, measured by bioassay in boys and girls in age groups comparabie to those in our study, have yielded conflicting results. Higher total gonadotropin levels in girls than in boys have been reported by Brown* but Fitschen and Clayton”

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106 1

found the opposite. Rifkind, Kulin, and Ross,lO using the Steelman-Pohley assay for FSH and the ventral prostate weight assay for LH, have recently shown that the mean urinary excretion of FSH was five times higher than that for LH in prepubertal children (pooled urine from boys and girls). There was a 2.5-fold increase in FSH; a 10.7-fold increase in LH between childhood and adulthood. The changes in the pituitary-gonadal relationship during pubescence and puberty are poorly understood. Data from urinary excretion studies have indicated that there is a progressive increase in 17-ketosteroids, testosterone, and estrogen excretionl*, lZ, I3 during puberty in boys, but dehydroepiandrosterone, a weak androgen derived primarily from the adrenal cortex, appears in the urine during an early stage of puberty.13 This is consistent with the finding of Beas and associatesI’ that during puberty the gonadal sex steroids become increasingly prominent, and the earliest changes in puberty seem to be due to an increased secretory activity of the adrenal cortex (e.g., the early growth of pubic and axillary hair in patients with ovarian agenesis). Menarche was clearly associated with a rapid rise in LH secretion against a relatively constant background of FSH secretion (Fig. 3). It is difficult to relate these findings to precise changes in estrogen secretion

Serum

FSH

levels

in puberty

137

since menarche may only reflect a level of estrogen secretion sufficient to induce endometrial bleeding. No doubt estrogens are secreted long before puberty; in fact, cyclic estrogen excretion has been noted in girls 1 to 2 years before menarche.*? Experimental studies of puberty in rats bear some relevance to the present data in humans. Ramirez and SawyerI and Kragt and Ganong16 have provided some insight into the dynamics of puberty. In female rats, vaginal opening (one of the first signs of puberty) was associated with an abrupt drop in hypothalamic luteinizing hormone releasing factorl”; this was accompanied by a sharp drop in pituitary LH concentration and an increase in LH in peripheral blood. Pituitary FSH content, on the other hand, rose to a peak prepubertally and then declined as sexual maturity was attained, but no acute changes occurred at the time of puberty itself.“” These data are consistent with the pattern of FSH and LH secretion in girls nearing puberty. Nonetheless, the precise mechanism in the initiation of puberty is unknown. The Littell, tistical review

authors express appreciation to Dr. A. S. Department of Biometry, for the staanalysis of the data, Dr. I. Rothchild for of the manuscript, and to Miss D. V.

Kearschner ful

technical

and Miss T. Vargo

for their

skill-

assistance.

REFERENCES

1. 2. 3.

4. 5.

6. 7.

8.

Midgley. A. R., Jr.: J. Clin. Endocrinol. 27: 295, 1967. Yen, S. S. C., Vicic, W. J., and Kearschner, D. V.: J. Clin. Endocrinol. 29: 382, 1969. Donovan, B. T., and van der Werff ten Bosch, J. J.: Physiology of Puberty, Baltimore, 1968, The Williams & Wilkins Company. Schalch, D. S., Bryson, M. F., and Lee, L. A.: Pediat. Res. 2: 308, 1968. (Abst.) Raiti, S., Johanson, A., Light, C., Migeon, C. J., and Blizzard, R. M.: Metabolism, 18: 234, 1969. Midgley, A. R., Jr., and Jaffe, R. B.: J. Clin. Endocrinol. 28: 1699, 1968. Peterson, N. T., Jr., Midgley, A. R., Jr., and Jaffe, R. B.: J. Clin. Endocrinol. 28: 1473, 1968. Brown, P. S.: J. Endocrinol. 17: 329, 1958.

9. 10. 11. 12. 13.

14.

15. 16.

Fitschen, W., and Clayton, B. E.: Arch. Dis. Childhood 40: 16, 1964. Rifkind, A. B., Kuhn, H. E., and Ross, G. T.: J. Clin. Invest. 46: 1925, 1967. Knorr, D.: Acta endocrinol. 54: 215, 1967. Nathanson, I. T., Towne, L. E., and Aub, J. C.: Endocrinology 28: 851, 1941. Steeno, O., Heyns, W., Van Baelen, H., Van Herle, A., and deMoor, P.: European J. Steroids 2: 273, 1967. Beas, F., Zurbrugg, R. P., Cara, J., and Gardner, L. I.: J. Clin. Endocrinol. 22: 1090, 1962. Ramirez, V. D., and Sawyer, C. H.: Endocrinology 78: 958, 1966. Kragt, C. L., and Ganong, W. F.: Endocrinology 82: 1241, 1968.