Gonadotrophin-independent puberty in a boy with a beta-HCG-secreting brain tumour

We report on a short-statured boy in whom therapy with recombinant human growth hormone was initiated at the age of 9.7 years for assumed idiopathic growth hormone deficiency. On recombinant human growth hormone, height improved from -1.9 (standard deviation score) to -0.9 within 1 year, and the patient entered puberty spontaneously at 10.7 years. At 11.6 years he showed low morning cortisol and thyroxine levels, but was otherwise well. He showed an inconspicuous growth, and puberty progressed adequately until the age of 13.4 years, when he developed signs of an increased intracranial pressure, and a suprasellar choriocarcinoma was diagnosed. This case confirms the fact that beta chorionic gonadotrophin secreting tumours will not be diagnosed by the characteristic clinical manifestation of gonadotrophin-independent puberty if they occur at a time when normal puberty is expected. Particularly, it raises the question of how often the CNS should be re-evaluated by magnetic resonance imaging in children with growth hormone deficiency and normal initial neuroradiological imaging, when they develop additional hormonal deficiencies but no other clinical symptoms of an intracranial process.     

Development of puberty in Large White boars in a humid tropical environment

The development of puberty in Large White boars raised and maintained in a humid tropical environment was studied histologically and by a preputial smear technique. The growth curves for the testes, epididymides and body weight were similar and exhibited a spurt between the ages of 150 and 180 days. The accessory sex glands increased slowly but steadily until the animals were about 180 days old at which time a marked increase in their growth rate was noted. Thus from morphological and histological assessment, puberty in these animals was placed between 150 and 180 days. The preputial smear technique was successfully applied in the boar. By this method, the animals were found to be 165.74 days old at puberty and to weigh 51.65 kg. These results further indicate that the development of puberty is genetically controlled and also imply that this could be slightly modified by the environment.     

Experience with growth hormone therapy in Turner syndrome in a single centre: low total height gain, no further gains after puberty onset and unchanged body proportions

The experience gained since 1987, through observation of 85 girls with Turner syndrome under growth hormone (GH) treatment, has enabled the analysis of one of the largest cohorts. Our results show that age, karyotype and height reflect the heterogeneity of the patients examined at our growth centre. In 47 girls, followed over 4 years on GH (median dose 0.72 IU/kg/week), the median age was 9.4 years and mean height SDS was -3.55 (Prader) and -0.14 (Turner-specific), while height and other anthropometrical parameters [weight, body mass index, sitting height (SH), leg length (LL) SH/LL, head circumference, arm span] were documented and compared to normative data as well as to Turner-specific references established on the basis of a larger (n = 165) untreated cohort from Tübingen. The latter data are also documented in this article. Although there was a trend towards normalization of these parameters during the observation period, no inherent alterations in the Turner-specific anthropometric pattern occurred. In 42 girls who started GH treatment at a median age of 11.8 years, final height (bone age >15 years) was achieved at 16.7 years. The overall gain in height SDS (Turner) from start to end of GH therapy was 0.7 (+/- 0.8) SD, but 0.9 (+/- 0.6) SD from GH start to onset of puberty (spontaneous 12.2 years, induced 13.9 years) and -0.2 (+/- 0.8) from onset of puberty to end of growth. Height gain did not occur in 12 patients (29%) and a gain of > 5 cm was only observed in 16 patients (38%). Height gain correlated positively with age at puberty onset, duration, and dose of GH, and negatively with height and bone age at the time GH treatment started. Final height correlated positively with height SDS at GH start and negatively with the ratio of SH/LL (SDS). We conclude that, in the future, GH should be given at higher doses, but oestrogen substitution should be done cautiously, owing to its potentially harmful effect on growth. LL appears to determine height variation in Turner syndrome and the potential to treat short stature successfully with GH.     

Early puberty: what is normal and when is treatment indicated?

Girls and boys who enter puberty before 8 and 9 years of age, respectively (corresponding to about -3 SDS), are arbitrarily considered to need referral for endocrine investigation. A recent report from the Lawson Wilkins Pediatric Endocrine Society suggested that the limit for investigation of girls and boys should be lowered to 7 and 8 years, respectively. For African-American girls, 6 years is the suggested age. This recommendation has been criticized. Although short stature is a common end result of precocious puberty, short- and long-term psychological symptoms may be more important, since several studies have indicated psychopathology in this patient group. Whether this can be prevented by gonadotropin releasing hormone agonist treatment remains to be shown. This review will highlight the psychological aspects of early puberty. In short, aspects other than height should also be evaluated when considering treatment of the early maturing child.     

Early influences on the tempo of puberty

Fetal growth retardation appears to be associated with an increased risk of premature adrenarche, early puberty, polycystic ovary syndrome and associated fertility problems. In a rat model of intrauterine growth retardation, based on ligation of the uterine arteries, the onset of puberty was delayed in female pups, with anovulation during the first cycle. The ovaries showed a lower number of follicles. The onset of puberty was also delayed in male pups. Testosterone production was lower in these growth-retarded rats compared with controls. The relationship between birth weight and the onset of puberty and pubertal progression in different cohorts of healthy children has been examined. In girls, no differences were observed in timing and progression of puberty, including age of menarche, between groups of different birth weights. In boys, a relatively delayed onset of puberty was observed in those with low birth weight, with a normally timed progression. In children with low birth weight, particularly boys, higher dehydroepiandrosterone levels were found compared with children with a normal birth weight, indicating an overactive adrenal gland in children with low birth weight. These data indicate that impaired fetal growth may have long-lasting effects on pubertal development. The fact that results of human studies on the relationship between fetal growth and the onset of puberty are often controversial may be explained by the heterogeneity of children born small for gestational age with respect to the intrauterine insult that they experience. From rat studies, it is clear that a serious intrauterine insult associated with growth failure can lead to dysregulation of puberty and gonadal function.     

Effect of pre-pubertal growth rate of Sohagi ram lambs on some physiological parameters and sexual behavioral patterns at puberty

Thirty healthy Sohagi ram lambs with an average age of 188.6±7.3 days were used to study the effect of pre-pubertal growth rate on some physiological parameters and sexual behavioral patterns at puberty. Ram lambs were divided into three groups (10 animals per each group) according to the previous growth rate until 6 months of age. Groups were marked as fast, medium and slow growing. Animal groups were housed in closed barns with access to an open area. Results showed that age and weight of ram lambs at puberty were significantly affected (P<0.05) by the pre-pubertal growth rate. Ram lambs in the fast growing group were reached to onset puberty firstly at 272.6 days with body weight (BW) 37.1 kg on average then ram lambs in medium group (284.8 days with BW 32.7 kg), while ram lambs in slow growing group were the last (314.1 days with BW 32.5 kg). Blood‎ testosterone‎ concentration at puberty was not significantly different among growing groups (1.494± 0.03 ng/ml on average, ranged from 1.287 to 1.902 ng/ml). Testes measurements from 6 months of age until puberty show that ram lambs in fast growing group had the highest values of testes length, circumference and volume followed by those in medium and slow growing group. Sexual behavioral observation showed that flehmen and mounting behavior were significantly higher for ram lambs in fast growing group (5.63 and 6.75 number/12h) than slow growing group (4.25 and 5.38 number/12h) while in medium growing group were intermediate (4.88 and 5.88 number/12h). From these findings, could be concluded that age, weight and sexual behavioral patterns of Sohagi ram lambs at puberty were affected by pre-pubertal growth rate, and the breeders should strive to achieve good growth rates for their lambs before puberty which led to improving reproductive performance.     

Blunted pubertal growth after leukemia: a new pattern of growth hormone insufficiency

Growth, age at menarche and spontaneous GH secretion were studied in girls after treatment for acute lymphoblastic leukemia (ALL). These girls had normal prepubertal growth but subnormal pubertal growth. Mean final height was 1 SD less than expected before puberty. The average age at menarche was significantly lower than the normal mean for Swedish girls. The mean 24-hour GH secretion was severely blunted and there was no increase during puberty. We suggest that girls treated for ALL, including CNS irradiation, have a relative GH insufficiency which becomes clinically obvious only when the girls cannot respond to the increased demands for GH in puberty.     

Testicular ultrasonogram pixel intensity during sexual development and its relationship with semen quality, sperm production, and quantitative testicular histology in beef bulls

This study was conducted to evaluate testicular ultrasonogram pixel intensity during sexual development in bulls and to determine its relationship with semen quality, sperm production, and quantitative testicular histology. Beef bulls (N = 152) were examined from 14 - 26 to 70 - 74 wk of age in four different years. Testicular echogenicity increased during sexual development, but the pattern of change differed among years. Echogenicity increased between 26 and 42 to 46 wk of age in 2 yr, but increased considerably earlier in the other 2 yr, reaching maximum values at 34 wk of age. Because increased echogenicity was likely associated with testicular changes leading to initiation of spermatogenesis, these differences were difficult to explain considering that age at puberty did not differ significantly among years. When data were evaluated according to age normalized to puberty, echogenicity started to increase 16 to 12 wk before puberty and reached maximum values 4 wk before or at puberty. These results indicate that a certain developmental stage of the testicular parenchyma must be reached before puberty and that the composition of the parenchyma remained consistent after puberty. Testicular echogenicity was associated with sperm production, seminiferous tubule and epithelium area, and sperm morphology, but the associations were not consistent. Testicular echogenicity was a good indicator of pubertal and mature status, but was not superior to scrotal circumference. In conclusion, although testicular ultrasonogram pixel intensity analysis might be useful for research purposes, clinical application of this technology in the present form for bull breeding soundness evaluation is not justifiable.     

中枢性性早熟对儿童生长发育的影响及其危险因素分析

摘要 目的：分析中枢性性早熟对儿童生长发育的影响及其危险因素。方法：选择我院自2020年1月至2023年1月收治的105例中枢性性早熟患儿作为观察组,另选同期的105例发育正常儿童作为对照组,比较两组生长发育指标、血清胰岛素样生长因子-1（IGF-1）、胰岛素样生长因子结合蛋白3（IGF-BP3）表达水平,对入组者膳食模式、生活情况、家庭状况进行问卷调查,使用单因素分析和多因素Logistic回归分析。结果：观察组身高、体重、身体质量指数、骨龄均大于对照组（P＜0.05）;观察组血清IGF-1、IGF-BP3表达水平均高于对照组（P＜0.05）;经单因素分析,午睡习惯、运动时间、亮灯睡觉、课业负担、经常使用塑料制品、成人洗漱护肤品、观看情感类电视、母亲学历、职业、初潮年龄,父母关系、陪伴、平衡膳食模式、高热量高脂膳食模式均与中枢性性早熟有关（P＜0.05）;经多因素Logistic回归分析,平衡膳食模式、有午睡习惯、运动时间长均是中枢性性早熟的保护因素（P＜0.05）,高热量高脂膳食模式、母亲初潮年龄小、父母关系不和睦、父母陪伴少均是中枢性性早熟的危险因素（P＜0.05）。结论：中枢性性早熟可影响儿童的生长发育进度,与高热量高脂膳食模式、母亲初潮年龄、父母关系和陪伴密切相关,应改善家庭关系,帮助儿童养成平衡膳食、午睡和运动的良好习惯,有益于儿童正常的生长发育。     

Reduced growth hormone secretion prolongs puberty but does not delay the developmental increase in luteinizing hormone in the absence of gonadal negative feedback

Previous studies have shown that the growth hormone (GH) axis is important for timing the later stages of puberty in female monkeys. However, it is not clear whether these growth-related signals are important for the initiation of puberty and early pubertal events. The present study, using female rhesus monkeys, used two approaches to answer this question. Experiment 1 tested the hypothesis that reduced GH secretion would blunt the rise in nocturnal LH secretion in young (17 mo; n = 7) but not older adolescent ovariectomized females (29 mo; n = 6). Reduced GH secretion was induced by treating females with the sustained release somatostatin analogue formulation, Sandostatin LAR (625 microg/kg). Morning (0900-0930 h) and evening (2200-2230 h) concentrations of bioactive LH were higher in older adolescent compared to young adolescent females. However, diurnal concentrations were not affected by the inhibition of GH secretion in either age group when compared to the placebo-treated, control condition. Experiment 2 tested the hypothesis that reduced GH secretion induced in young juvenile females would delay the initial increase in nocturnal LH secretion and subsequent early signs of puberty. In order to examine this hypothesis, puberty in control females (n = 7) was compared to those in which puberty had been experimentally arrested until a late adolescent age (29 mo) by the use of a depot GnRH analogue, Lupron (750 microg kg(-1) mo(-1); n = 7). Once the analogue treatment was discontinued, the progression of puberty was compared to a group treated in a similar fashion but made GH deficient by continuous treatment with Sandostatin LAR (n = 6). Puberty occurred as expected in control females with the initial rise in evening LH at 21 mo, menarche at 22 mo, and first ovulation at 30 mo. As expected, Lupron arrested reproductive maturation, but elevations in morning and evening LH and menarche occurred within 2 mo of the cessation of Lupron in both Lupron and Lupron-GH-suppressed females. In contrast, first ovulation was delayed significantly in the Lupron-GH-suppressed females (41 mo) compared to the Lupron-only females (36 mo). These data indicate that within this experimental model, reduced GH secretion does not perturb the early stages of puberty but supports previous observations that the GH axis is important for timing the later stages of puberty and attainment of fertility. Taken together, the data indicate that factors that reduce GH secretion may have a deleterious effect on the completion of puberty.     

Pulsatile infusion of luteinizing hormone-releasing hormone induces precocious puberty (vaginal opening and first ovulation) in the immature female guinea pig

Previously we have hypothesized that an increase in luteinizing hormone-releasing hormone (LHRH) due to hypothalamic maturation is the key factor controlling the onset of puberty. This led to the working hypothesis that precocious puberty would be induced if LHRH is administered with an appropriate protocol. Thus, effects of pulsatile infusion of LHRH on the onset of first vaginal opening and first ovulation in immature female guinea pigs were studied. Luteinizing hormone-releasing hormone in hourly pulses of either 5 ng or 50 ng was infused through a chronically implanted jugular catheter for 9-29 days starting at 20 days of age. For the control experiment saline was infused in a similar manner. Infusion of 5 ng LHRH/h resulted in significantly earlier (P less than 0.001) ages at first vaginal opening (24.7 +/- 0.9 days) and at first ovulation (28.8 +/- 0.9 days) compared to saline controls (first vaginal opening 53.3 +/- 6.8 days; first ovulation 55.2 +/- 6.5 days). Infusion with a 10-fold higher LHRH dose (50 ng/h) also advanced the age at first vaginal opening (25.3 +/- 0.7 days), but precocious ovulation was no longer induced (53.7 +/- 5.3 days). Interestingly, LHRH infusion with the high dose resulted in a prolonged period of vaginal opening and cornification without ovulation. These results indicate that 1) pulsatile infusion of a small amount of LHRH with a constant frequency induces precocious puberty in a laboratory rodent, and 2) infusion of LHRH with a dose higher than the effective dose for the induction of early puberty results in a persistent estrous anovulatory syndrome. Therefore, the present study not only supports our hypothesis that an increase in endogenous LHRH release is responsible for the onset of puberty, but also further suggests that excessive release of LHRH or abnormal patterns of LHRH release may be involved in the etiology of the anovulatory persistent estrus syndrome.     

Ascertainment and treatment of delayed puberty

The majority of patients with pubertal delay, can be classified as having primary pubertal delay (constitutional delay of growth and puberty, CDGP), although any child with a chronic disease could present with delayed puberty. In contrast, children with hypogonadism, either hyper- or hypogonadotropic, exhibit a total absence of pubertal development. Hence, early evaluation of these patients should be performed. Delay of puberty leads to psychological problems, secondary to short stature and/or delay in the acquisition of secondary sex characteristics and the reduction of bone mass. Although the final height in patients with CDGP is usually normal, some of these patients do not reach the third percentile or remain in the lowest part of the growth chart according to familial height. The most common reason for treating CDGP patients, usually with sex steroids, is for psychological difficulties and for loss of bone mineralization. Treatment must be individualized. Therapeutic options and new drugs will be discussed. Appropriate treatment and adequate nutritional intake are indicated in patients with delayed puberty due to chronic illness. In patients with hypo- or hypergonadotropic hypogonadism, puberty must be induced or completed. Different treatments (GnRH analogues, gonadotropins and sex steroids), and the main objectives are discussed.     

Gonadotrophin secretion in prepubertal bull calves born in spring and autumn

The reproductive development of bull calves born in spring and autumn was compared. Mean serum LH concentrations in calves born in spring increased from week 4 to week 18 after birth and decreased by week 24. In bull calves born in autumn, mean LH concentrations increased from week 4 to week 8 after birth and remained steady until week 44. LH pulse amplitude was lower in bull calves born in autumn than in calves born in spring until week 24 of age (P < 0.05). There was a negative correlation between LH pulse frequency at week 12 after birth and age at puberty in bull calves, irrespective of season of birth, and LH pulse frequency at week 18 also tended to correlate negatively with age at puberty. Mean serum FSH concentrations, age at puberty, bodyweight, scrotal circumference, testes, prostate and vesicular gland dimensions, and ultrasonographic grey scale (pixel units) were not significantly different between bull calves born in autumn and spring. However, age and body-weight at puberty were more variable for bull calves born in autumn (P < 0.05). In a second study, bull calves born in spring received either a melatonin or sham implant immediately after birth and at weeks 6 and 11 after birth. Implants were removed at week 20. Mean LH concentrations, LH pulse frequency and amplitude, mean FSH concentrations and age at puberty did not differ between the two groups. No significant differences between groups in the growth and pixel units of the reproductive tract were observed by ultrasonography. In conclusion, although there were differences in the pattern of LH secretion in the prepubertal period between bull calves born in autumn and spring, the postnatal changes in gonadotrophin secretion were not disrupted by melatonin treatment in bull calves born in spring. Reproductive tract development did not differ between calves born in spring and autumn but age at puberty was more variable in bull calves born in autumn. LH pulse frequency during the early prepubertal period may be a vital factor in determining the age of bull calves at puberty.     

The Method of ABA Application Affects Salt Stress Responses in Resistant and Sensitive Potato Lines

The phytohormone abscisic acid (ABA) has been proposed to act as a mediator in plant responses to a range of stresses, including salt stress. Most studies of ABA response apply ABA as a single dose. This may not resemble the prolonged increasing endogenous ABA levels that can occur in association with slowly increasing salinity stresses in nature or field situations. Salt stress response based on method of ABA application was examined in four potato genotypes of varying salt stress resistance: the sensitive ABA-deficient mutant and its normal sibling, a resistant genotype line 9506, and commercial cultivar ‘Norland’ of moderate resistance. ABA was applied by root drench at 0, 50, 75, or 100 μM concentrations through a single dose, or by slowly increasing multiple ABA doses in a sand-based growing system under greenhouse conditions. Salt tolerance was then evaluated after 2 weeks of exposure to 150–180 mM NaCl stress. The method of ABA application had a marked effect on the responses to salt stress. Plant responses to the method of ABA application were differentiated according to (1) growth rate, (2) root water content, and (3) apparent shoot growth response. Under a single dose, growth rate increased in all genotypes under salt stress, whereas slowly increasing multiple ABA applications generally maintained stable growth rates except in the ABA-deficient mutant where there was an upward growth trend. Percent root water content was elevated only under slowly increasing multiple ABA doses in two genotypes, whereas none of the single-dose treatments induced any change. The single ABA dose enhanced vertical growth, whereas the slowly increasing multiple ABA dose applications enhanced lateral shoot growth. Because exogenous application is still an artificial system, endogenous ABA was supplied through grafting of ABA-deficient mutant scions onto rootstocks with known elevated ABA levels. Multiple exogenous ABA applications as low as 50 μM elicited similar shoot water content responses as grafting treatments without ABA application in the mutant genotype but had no effect on the ABA normal sibling. Shoot dry weight was significantly increased through grafting over all exogenous ABA treatments. Our study further indicates that the method of ABA application regime in itself can alter plant responses under salt stress and that certain application regimes may reflect responses to elevated endogenous levels of ABA.     

Evidence that a decrease in testosterone negative feedback mediates the pubertal increase in luteinizing hormone pulse frequency in male ferrets

Neuroendocrine mechanisms regulating luteinizing hormone (LH) secretion during puberty were investigated in intact male ferrets and ferrets castrated at 8 wk of age that received s.c. implants of either empty or testosterone-filled Silastic capsules. To synchronize puberty onset among individuals, ferrets were exposed to short days between 8 and 16 wk of age, and then transferred to long days. Testis growth began in intact ferrets soon after photoperiod transition. Blood samples were obtained at 11, 15, 19, and 23 wk of age. LH pulse frequency was low in intact ferrets at 11 and 15 wk of age (less than or equal to 0.27 pulses/h), but rose to 0.94 pulses/h by 23 wk of age. No age-related increase in LH pulse frequency was observed in untreated castrated ferrets. LH pulses were rare in testosterone-treated castrated ferrets at 11 and 15 wk of age; but by 23 wk of age, frequency rose to 0.33 pulses/h. Thus, testis maturation in ferrets is accompanied by a dramatic increase in LH pulse frequency. No steroid-independent developmental increase in LH pulse frequency occurs in castrated ferrets. Furthermore, doses of testosterone that prevent LH secretion in young castrated ferrets do not as effectively suppress LH pulses in older ferrets. These data suggest that a decrease in the efficacy of testosterone negative feedback mediates the pubertal rise in LH pulse frequency in male ferrets.     

Pubertal growth of the short normal girl

OBJECTIVES: To determine the timing, magnitude and duration of the pubertal spurt for short normal and average height girls, to compare these with Tanner's standard and to investigate predictors of pubertal growth. METHODS: The growth of 46 short normal and 55 control girls, identified at school entry, was monitored throughout puberty. Height and weight were measured at 6-month intervals from which body mass index (BMI) was derived. Annual velocities were calculated and used to estimate the age and magnitude of peak height velocity (PHV). Age of menarche was recorded to the nearest month. Parents provided information on the child's medical and social history. RESULTS: The mean age at PHV, the magnitude of PHV and age at menarche were similar for both groups and close to Tanner's 50th centile values. Pre-pubertal BMI predicted age at menarche for short and control girls, accounting for 17% of the variance. There was a tendency for early maturing girls of average stature to have greater PHV. However, this relationship was not observed in short girls, nor did any other variable, genetic or environmental, predict the timing or magnitude of their pubertal spurt. CONCLUSIONS: Delayed puberty in short normal girls is unlikely and their growth during puberty is comparable to girls of average height. The pubertal variables measured remain close to Tanner's original standards for both groups, suggesting the lack of a secular trend towards earlier puberty in girls. The onset of menstruation is influenced by pre-pubertal BMI. However, the clinician should be aware that short normal girls have normal pubertal growth and that no genetic or environmental variable can predict the timing or magnitude of their growth spurt.     

STIMULATION OF DNA SYNTHESIS BY ISOPROTERENOL IN RAT SUBMANDIBULAR GLAND DURING POSTNATAL GROWTH

The post-natal growth of rat submandibular gland and the effect of isoproterenol on this process were studied. Between 2 and 42 days of age the DNA content of the gland increased linearly but the increase in RNA and protein content was more rapid after 29 days of age. The RNA: DNA and protein: DNA ratio increased linearly with age. The proliferative activity, measured by the incorporation of tritiated thymidine, was maximum in the gland of 7-day-old rats. It declined steadily to a low level in 42-day-old rats. A single injection of isoproterenol had no effect on thymidine incorporation in 2-day-old rats. The drug, however, stimulated DNA synthesis in older animals and the degree of stimulation was inversely correlated with the proliferative activity in control rats. Small doses of isoproterenol given to rats for 4 days between 2 and 5 days of age produced a hypertrophy of the submandibular gland. The same treatment between 7 and 10 days of age caused both hypertrophy and hyperplasia of the gland. It is concluded that both the regulation of growth and the regulation of induced cell proliferation are a function of cellular differentiation and that cell proliferation can be induced only in cells that reached a certain degree of differentiation.     

Growth and timing of puberty: reciprocal effects.

Based on the analysis of the pubertal growth spurt and final height in different pathological conditions, this paper provides evidence that variations in age at onset of puberty have a major influence on the subsequent acceleration of the growth rate but a minor impact on final height. A reciprocal effect of the growth rate on the timing of onset of puberty is also suggested by a number of clinical observations.     

Effect of exercise on the onset of puberty, gonadotropins, and ovarian inhibin

Swimming 6 h/day from 11 days of age led to a significant delay of the onset of puberty of female rats compared with the sedentary group. Rats who were in contact with water but without the energy expenditure due to exercise (paddlers) had their vaginal opening in a middle point between control and exercising rats. Vaginal opening occurred at different ages but at a same body weight. Exercise and stress led to a marked decrease of the body weights between 19 and 40 days of age. Serum luteinizing hormone and follicle-stimulating hormone were increased with the exercise program at 30 days of age, whereas no significant differences between groups in serum gonadotropins were observed at 50 days of age. Only the anterior pituitary luteinizing hormone content was increased by exercise in adult rats. Total ovarian proteins were significantly reduced by stress and to a greater degree by exercise. Ovarian inhibin activity is not modified by exercise at 30 days of age, whereas it increased significantly in the exercising group at 50 days of age and to a lesser degree in paddlers. It is therefore suggested that the onset of puberty in rats is dependent on a critical weight and that exercise and stress can delay the onset of puberty. This delay could be explained by a deficiency of hormonal maturational process while exercising until sexual maturity alters the inhibin activity, which suggests that inhibin could play a major role for the normal reproductive function and this could possibly explain the menstrual disturbances in the female athlete.