Androgen and estrogen treatments alter steady state messengers RNA (mRNA) levels of testicular steroidogenic enzymes in the rainbow trout, Oncorhynchus mykiss

Recent investigations have shown that estrogens have profound inhibitory effects on steroidogenic enzyme gene expressions before and after testicular differentiation in the rainbow trout, Oncorhynchus mykiss. This present study bring new data on juvenile rainbow trout treated with estrogens and androgens. Following a 8 days oral treatment of juvenile male with 17alpha-ethynyl-estradiol (EE2, 20 mg/kg diet) or 11beta-hydroxyandrostenedione (11betaOHDelta4, 10 mg/kg diet), we observed a fast and marked decrease of steady-state mRNA levels for 3betaHSD, P450scc, P450c17, and P450c11 enzymes in the testis. After completion of these treatments, mRNA levels of these enzymes remained low in EE2 treated males whereas in 11betaOHDelta4 treated males they recovered their initial levels in 8 days. This demonstrate that both androgen and estrogen treatments have profound effects on testicular steroidogenesis by decreasing steroid enzymes steady-state mRNA. After in vitro incubation of testicular explants with 17beta-estradiol (E2, 600 ng/ml of medium), we also observed a decrease of mRNA levels for 3betaHSD and P450c11. This suggest that estrogens effects could be triggered, at least to some extend, directly on the testis. We also investigated the hypothesis of a negative feedback of steroids on follicle stimulating hormone (FSH) secretion, but FSH plasmatic levels in treated fish did not showed any significant decrease. This demonstrate that FSH is not implied in this steroids inhibition of steroidogenic enzymes gene expression.     

Rôle du peptide vasoactif intestinal (VIP) dans la stéroïdogenèse et le vieillissement testiculaire

VIP (vasoactive intestinal peptide) neuropeptide has long been considered to be putative regulator of testicular functions.In vitro evidence suggests that VIP could play an important role in testosterone biosynthesis. However, the endogenous role of VIP on testicular functions remained to be demonstrated. In C57BL/6 mice exhibiting complete disruption of the VIP gene, the authors observed that male fertility remained intact but serum testosterone levels were lower than those of WT littermates. At the age of 4 months, this phenotype was accompanied by reduced steroidogenesis due to inhibition of the expression of StAR (steroidogenic acute regulatory protein) and 3ßHSD (3ß-hydroxysteroid dehydrogenase) in the testis. In addition, serum levels of FSH (Follicle-stimulating hormone) but not LH (Luteinizing hormone) were reduced in young KO males. Testicular anatomy also revealed a subtle but significantly higher percentage of degenerated seminiferous tubules in 4-month-old VIP-/-animals compared to WT. In aging animals (15 months old), control males showed typical testicular aging including severe degeneration of seminiferous tubules, a dramatic decrease in serum testosterone levels and a reduction in StAR and 3ß-HSD gene expression. In age-matched VIP-/-males, serum levels of testosterone and steroidogenic enzymes were still very low. Interestingly, in contrast with young mice, testicular degeneration at 15 months was significantly less severe marked in VIP-/-mice than in WT mice. Altogether, these results suggest that: 1) VIP is an important factor for regulating testosterone biosynthesis and FSH secretion and 2) VIP regulates testicular aging.     

Reproductive hormone profiles in captive male orangutans: Implications for understanding developmental arrest

For many years researchers have described some male orangutans as “subadult.” These males are of adolescent to adult age and are reproductive, but have little to no secondary sexual trait development. Until now the only endocrine study of this arrest of secondary sexual trait development was performed by Kingsley (1982, 1988). She found that “subadult” or arrested males have lower testosterone levels than similar age developing adolescents or adult males. In this study, urine samples were collected over a two-year period from 23 captive male orangutans in order to more fully define male endocrine profiles. Three study males were juveniles, seven were arrested adolescents, six were developing adolescents, and seven were mature adults. Morning samples were analyzed by radioimmunoassay for levels of testicular steroids and gonadotropins and group hormone profiles were compared by analysis of variance. Results illustrate that arrested adolescent orangutans have significantly lower testosterone and dihydrotestosterone (DHT) levels than developing adolescents, but significantly higher levels than juveniles. Luteinizing hormone (LH) levels also differed between arrested and developing adolescents, with arrested males having lower levels. However, follicle stimulating hormone (FSH) levels were similar in both morphs of adolescent male. The overall hormone profiles for arrested and developing adolescent male orangutans suggest that arrested males lack levels of LH, testosterone, and DHT necessary for development of secondary sexual traits. However, they have sufficient testicular steroids, LH, and FSH to fully develop primary sexual function and fertility. These endocrine data help define alternative developmental pathways in male orangutans. The authors discuss the relationship between these developmental pathways and male orangutan reproductive strategies, and hypothesize about their prepubertal socioendocrine determination. Am J Phys Anthropol 109:19–32, 1999. © 1999 Wiley-Liss, Inc.     

X inactivation as a source of behavioural differences in monozygotic female twins.

Although members of monozygotic twin pairs are identical in genome sequence, they may differ in patterns of gene expression. One early and irreversible process affecting gene expression, which can create differences within pairs of female monozygotic twins, is X inactivation - one twin can express mainly paternally-received genes on the X chromosome while the other twin expresses mainly maternally-received genes. It follows that non-identical X chromosome expression may cause female monozygotic twins to correlate less strongly than male monozygotic twins on complex behavioural traits affected by X-linked loci. We tested this hypothesis using data from around 4000 same-sex twin pairs on 9 social, behavioural and cognitive measures at ages 2, 3 and 4. Consistent with our hypothesis, monozygotic males were generally more similar than monozygotic females. Three of four significant differences were in traits showing higher correlations in males than females, and these traits - prosocial behaviour, peer problems, and verbal ability - have all been proposed previously in the literature as being influenced by genes on the X chromosome. Interestingly, dizygotic twins showed the reverse pattern of correlations for similar variables, which is also consistent with the X inactivation hypothesis; taken together, then, our monozygotic and dizygotic results suggest the presence of quantitative trait loci on the X chromosome.     

Fathering of Dizygotic Twins and Risk of Prostate Cancer: Nationwide,Population-Based Case-Control Study

Background

An association between male fertility and risk of prostate cancer has been suggested, possibly through lower androgen levels in subfertile men. We evaluated male fertility in relation to risk of prostate cancer by assessing the frequency of fathering of dizygotic twins, a marker of high fertility, among cases of prostate cancer and controls.

Methods

We performed a case-control study in Prostate Cancer data Base Sweden (PCBaSe), a nationwide, population-based cohort. PCBaSe was linked to the Swedish twin register for information on zygosity for same-sex twins and to other nationwide health care registers and demographic databases for information on socioeconomic factors, comorbidity, and tumor characteristics for 96 301 prostate cancer cases and 378 583 matched controls. To account for the influence of in vitro fertilization on dizygotic twinning, analyses were restricted to men who had fathered children before 1991, when in vitro fertilization was still uncommon in Sweden.

Results

1 112 cases and 4 538 controls had fathered dizygotic twins. Men with dizygotic twins had no increased risk of prostate cancer compared to fathers of singletons; neither for total prostate cancer odds ratio (OR) 0.95(95% CI 0.89–1.02), nor for any risk category, OR 0.97 (95% CI 0.84–1.12) for low-risk disease, and OR 1.04 (95% CI 0.90–1.22) for metastatic disease.

Conclusion

The lack of association between fathering of dizygotic twins and prostate cancer risk give no support for an association between male fertility and prostate cancer risk.     

The role of the placenta in variability of fetal exposure to cocaine and cannabinoids: a twin study.

There is wide variability in the reported adverse fetal effects of cocaine and cannabinoids. The causes of this variability are largely unknown. We hypothesized that variability in placental handling of drugs affect fetal exposure. We used twin pregnancies as a paradigm to address the role of the placenta in this variability. We analyzed hair or meconium samples taken from dizygotic and monozygotic twins exposed in utero to illicit drugs. Out of 12 pairs, 5 had negative levels in both twins, and seven pairs of twins had chemical evidence of fetal exposure to cocaine (n = 5) or cannabinoids (n = 2). The one known monozygotic pair of twins had almost identical levels of cocaine. In contrast, the six dizygotic pairs had large disparities in either cocaine or cannabinoid concentrations. In three of these six dizygotic pairs, levels of cocaine (n = 2) or canabinoids (n = 1) were undetectable in one twin while positive in the other. Given that twins are theoretically exposed to similar maternal drug levels, our findings suggest that the placenta may have a major role in modulating the amounts of drug reaching the fetus.     

Twin births to mothers who are twins: a registry based study.

OBJECTIVES: To estimate the risk of having twin infants for mothers who are twins; to investigate the genetic influence on twinning. DESIGN: Retrospective study of multiple births in two nationwide registries. SETTING: Sweden. SUBJECTS: Multiple births among 31,586 deliveries between 1973 and 1991 to women who were twins. MAIN OUTCOME MEASURES: Numbers of monozygotic and dizygotic twin births expected and estimated. RESULTS: Women who are dizygotic twins have a moderately increased risk of having twins (relative risk 1.30, 95% confidence interval 1.14 to 1.49) which seems to be completely the result of dizygotic twinning. When a mother is a monozygotic twin, her risk of having twins of the same sex is significantly increased (1.47; 1.10 to 1.97). This is the result of an excess of monozygotic twins (39 pairs estimated, 18 expected). CONCLUSIONS: Women who are twins have an increased risk of giving birth to twins. Genetic components of monozygotic and dizygotic twinning seem to be independent.     

Does higher concordance in monozygotic twins than in dizygotic twins suggest a genetic component?

It is widely regarded that twins can be used as a natural experiment to subject hypotheses to empirical testing regarding the contributions of genetic factors to phenotypic variability in human traits, especially behavioral traits. In genetic epidemiology, a higher concordance rate in monozygotic (MZ) twins than in dizygotic (DZ) twins is often taken as prima facie evidence for a genetic component. While twins studies have been used to estimate the contributions of genetic factors to phenotypic variability in human traits, the corresponding methodology that allows the estimation entails several crucial assumptions. The most critical is that MZ and DZ twins are equally similar environmentally. Although MZ twins are genetically more similar than DZ twins, they are often environmentally more similar. This paper demonstrates that, even in the complete absence of any genetic factor and of any biases, the greater environmental similarity alone in MZ twins can result in higher concordance rate in MZ twins than in DZ twins. This is especially true when there are multiple environmental factors, which may have multiple exposure levels and/or interact strongly, although each of them may be of low risk. This may serve as a sobering antidote to the uncritical reliance on twin studies without examining the validity of the underlying assumptions.     

Skeletal maturity and bone growth in twins

Heritability of skeletal maturity and bone growth is discussed on the basis of intrapair resemblances (correlation coefficients) and differences (revised percent deviations) in mono- and dizygotic twins and random pairs of unrelated children. A series of 1072 radiographs of the right hand and wrist in 63 male and 70 female pairs of monozygotic twins, and 25 male and 21 female pairs of dizygotic twins aged 12 to 18 years studied longitudinally in Tokyo were used. Skeletal maturity based on the TW2 age suggests higher heritability than bone growth based on the second metacarpal dimensions. In the latter, length has higher heritability than width and cortical thickness. A dosage effect seems to be suggested in width and some indices in the second metacarpal, but is not confirmed in skeletal maturation.     

Seasonally and experimentally induced changes in testicular function of the Australian bush rat (Rattus fuscipes)

Serum concentrations of LH, FSH and testosterone were measured monthly throughout the year in male bush rats. Testicular size and ultrastructure, LH/hCG, FSH and oestradiol receptors and the response of the pituitary to LHRH were also recorded. LH and FSH rose in parallel with an increase in testicular size after the winter solstice with peak gonadotrophin levels in the spring (September). The subsequent fall in LH and FSH levels was associated with a rise in serum testosterone which reached peak levels during summer (December and January). In February serum testosterone levels and testicular size declined in parallel, while the pituitary response to an LHRH injection was maximal during late summer. The number of LH/hCG, FSH and oestradiol receptors per testis were all greatly reduced in the regressed testes when compared to active testes. In a controlled environment of decreased lighting (shortened photoperiod), temperature and food quality, the testes of sexually active adult males regressed at any time of the year, the resultant testicular morphology and endocrine status being identical to that of wild rats in the non-breeding season. Full testicular regression was achieved only when the photoperiod, temperature and food quality were changed: experiments in which only one or two of these factors were altered failed to produce complete sexual regression.     

Inhibin B levels in adolescents and young adults with type 1 diabetes

OBJECTIVE/METHODS: To assess exocrine and endocrine testicular function in subjects with diabetes, we evaluated serum inhibin B, gonadotrophins and testosterone levels in 33 male adolescent and young adult patients affected by type-1 diabetes (age 21.0 +/- 5 years; range 14.2-33.3), with a mean disease duration of 12.7 +/- 5.8 years (range 1.5-25.3) and various metabolic control (HbA1c 7.8 +/- 1.5%; range 5.5-13.2) and compared them with those of an age-matched group of 36 healthy control subjects (age 19.5 +/- 4.1 years; range 13.6-28.1). Both patients and controls had a testicular volume >or=15 ml. Inhibin B was measured by ELISA method. RESULTS/CONCLUSION: Diabetics and controls had comparable inhibin B (203 +/- 74 vs. 221 +/- 69 pg/ml, respectively) and follicle-stimulating hormone (FSH) levels, while luteinizing hormone (LH) and testosterone levels were significantly higher in the diabetic group. Inhibin B was negatively correlated both in patients and controls with FSH, while a negative correlation with LH was found only in the diabetic group. We conclude that our young diabetic males, after a mean disease duration of 12 years and various metabolic control, had inhibin B and FSH levels comparable to those of normal subjects. Therefore, they seem to have a regular testicular function and in particular a normal seminiferous tubule/Sertoli cell activity despite sustained hyperglycemia.     

Genetic influence on human lifespan and longevity

There is an intense search for longevity genes in both animal models and humans. Human family studies have indicated that a modest amount of the overall variation in adult lifespan (approximately 20–30%) is accounted for by genetic factors. But it is not known if genetic factors become increasingly important for survival at the oldest ages. We study the genetic influence on human lifespan and how it varies with age using the almost extinct cohorts of Danish, Finnish and Swedish twins born between 1870 and 1910 comprising 20,502 individuals followed until 2003–2004. We first estimate mean lifespan of twins by lifespan of co-twin and then turn to the relative recurrence risk of surviving to a given age. Mean lifespan for male monozygotic (MZ) twins increases 0.39 [95% CI (0.28, 0.50)] years for every year his co-twin survives past age 60 years. This rate is significantly greater than the rate of 0.21 (0.11, 0.30) for dizygotic (DZ) males. Females and males have similar rates and these are negligible before age 60 for both MZ and DZ pairs. We moreover find that having a co-twin surviving to old ages substantially and significantly increases the chance of reaching the same old age and this chance is higher for MZ than for DZ twins. The relative recurrence risk of reaching age 92 is 4.8 (2.2, 7.5) for MZ males, which is significantly greater than the 1.8 (0.10, 3.4) for DZ males. The patterns for females and males are very similar, but with a shift of the female pattern with age that corresponds to the better female survival. Similar results arise when considering only those Nordic twins that survived past 75 years of age. The present large population based study shows genetic influence on human lifespan. While the estimated overall strength of genetic influence is compatible with previous studies, we find that genetic influences on lifespan are minimal prior to age 60 but increase thereafter. These findings provide a support for the search for genes affecting longevity in humans, especially at advanced ages.     

Intercellular communication between Sertoli cells and Leydig cells in the absence of follicle-stimulating hormone-receptor signaling

Effective interactions among the various compartments of the testis are necessary to sustain efficiency of the spermatogenic process. To study the intercellular communication between the Sertoli and Leydig cells in the complete absence of FSH receptor signaling, we have examined several indices of Leydig cell function in FSH receptor knockout (FORKO) mice. The serum testosterone levels were reduced in the 3- to 4-mo-old adult FORKO males compared to wild-type mice despite no significant alteration in circulating LH levels. Treatment with ovine LH resulted in a dose-dependent increase in serum testosterone levels in all three genotypes (+/+, +/-, and -/-). However, the response in FORKO males was significantly reduced. Similarly, the total intratesticular testosterone per testis was also lower, but the intratesticular testosterone per milligram of testis was significantly elevated in the FORKO males. Western blot analysis revealed an apparent higher expression of the enzyme 3beta-hydroxysteroid dehydrogenase (3beta-HSD) as well as LH-receptor density in the testis of FORKO males. Immunohistochemistry also showed an increase in the intensity of 3beta-HSD staining in the testicular sections of FORKO males. Although LH receptor binding increased per unit weight in FORKO mice, the total LH binding remained the same in all genotypes. Taken together, the results of the present study suggest that, in the absence of FSH receptor signaling, the testicular milieu is altered to affect Leydig cell response to LH such that circulating testosterone is reduced in the adult mutant. Studies are currently under way to understand the mechanisms underlying this phenomenon.     

Effects of accelerating growth on the onset of puberty in male mice

Sexual maturation was evaluated in male mice subjected to prenatal and preweaning overnutrition induced by reduction of litter size in embryonic and post-natal life. From birth to adulthood body weight was higher in overfed males than in controls. Plasma and testicular testosterone levels followed a similar pattern in normally fed and overfed males. Adult gonadotrophin levels were attained at 30 (FSH) and 40 (LH) days in controls and as soon as 20 days in overfed males. First fertile matings occurred at the same age in both groups. Overnourished males attained puberty when weighing considerably more than controls (34.7 +/- 0.4 vs. 29.4 +/- 0.3 g). The 30-day-old overfed males, which have attained the critical pubertal body weight of controls, were sexually immature. The data showed that in male mice puberty does not seem to be triggered by the attainment of a critical body weight.     

Brain and gonadal aromatase activity and steroid hormone levels in female and polymorphic males of the peacock blenny Salaria pavo

In the peacock blenny Salaria pavo large males with well-developed secondary sexual characters establish nests and attract females while small “sneaker” males mimic female sexual displays in order to approach the nests of larger males and parasitically fertilize eggs. These alternative reproductive tactics are sequential, as sneakers irreversibly switch into nesting males. This transition involves major morphologic and behavioral changes and is likely to be mediated by hormones. This study focuses on the role of aromatase, an enzyme that catalyses the conversion of androgens into estrogens, in the regulation of male sexual polymorphism in S. pavo. For this, sex steroid plasma levels and aromatase activity (AA) in gonads, whole brain and brain macroareas were determined in sneakers, transitional males (i.e. sneakers undergoing the transition into nesting males), nesting males and females collected in the field. AA was much higher in ovarian tissue than in testicular tissue and accordingly circulating estradiol levels were highest in females. This supports the view that elevated AA and estradiol levels are associated with the development of a functional ovary. Transitional males are in a non-reproductive phase and had underdeveloped testes when compared with sneakers and nesting males. Testicular AA was approximately 10 times higher in transitional males when compared with sneakers and nesting males, suggesting high AA has a suppressive effect on testicular development. Nesting males had significantly higher plasma levels of both testosterone (T) and 11-ketotestosterone when compared with the other male morphs and previous studies demonstrated that these androgens suppress female-like displays in sneakers. In the brain, AA was highest in macroareas presumably containing hypothalamic nuclei traditionally associated with the regulation of reproductive behaviors. Overall, females presented the highest levels of brain AA. In male morphs AA increased from sneakers, to transitional males, to nesting males in all brain macroareas. These results suggest that the transition into the nesting male tactic is accompanied both by an increase in testicular androgen production and by a higher conversion of androgens into estrogens in the brain. The increase in androgen production is likely to mediate the development of male secondary sexual characters while the increase in brain AA may be related to the behavioral changes associated with tactic transition.     

Feedback regulation of gonadotropic hormone secretion in neonatal pigs

The effect of castration and of administration of charcoal-treated porcine follicular fluid (pFF) containing inhibin-like activity on plasma concentration of gonadotropic hormones was studied in neonatal pigs. Plasma follicle-stimulating hormone (FSH) concentration averaged 25.1 +/- 1.5 ng/ml (mean +/- SEM) in 1-wk-old females and gradually declined to 20.2 +/- 0.7 ng/ml 6 wk later. Ovariectomy did not significantly influence plasma FSH concentration. In males, concentration averaged 8.0 +/- 0.7 ng/ml before castration but rose significantly within 2 days after castration. Injection of luteinizing hormone-releasing hormone (LHRH) did not influence plasma FSH concentrations in intact males, but did in females and in 7-wk-old males castrated at 1 wk. Plasma luteinizing hormone (LH) concentrations in 1-wk-old females (2.2 +/- 0.4 ng/ml) gradually declined and were not influenced by castration. Concentrations of plasma LH in 1-wk-old male piglets (2.8 +/- 0.7 ng/ml) were not significantly influenced by castration within 2 days but were significantly higher 6 wk later. LHRH induced a significant rise in plasma LH concentrations in all animals. Injection of pFF resulted in a decline of plasma FSH concentrations in intact and castrated males and in intact females, but did not influence plasma LH concentrations. These data demonstrate a sex-specific difference in the control of plasma FSH, but not in plasma LH concentration in the neonatal pig. Plasma FSH concentrations, but not plasma LH concentrations, are suppressed by testicular hormones in 1-wk-old piglets. Plasma FSH concentrations can be suppressed in both neonatal male and female pigs by injections of pFF.     

Effects of exogenous testosterone on testicular luteinizing hormone and follicle-stimulating hormone receptors during aging

During aging, the male Japanese quail exhibits a loss of fertility, increased morphological abnormalities in the testes, and a higher incidence of Sertoli cell tumors. Although there is a coincident loss of reproductive behavior, plasma androgen levels remain high until testicular regression occurs in association with senescence. The purpose of this study was to compare mean specific binding of chicken luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as a measure of testicular receptors during identified stages during aging. Males were categorized according to age (young = 9 months, middle aged = 24 months, or old = 36+ months) and sexual behavior (active or inactive). Testicular samples were collected immediately after perfusion with 4% paraformaldehyde from the following groups: young active (n = 8), young photoregressed (n = 5), young photoregressed plus testosterone implant (n = 4), middle-aged active (n = 8), middle-aged inactive (n = 4), old inactive (n = 5), and old inactive plus testosterone implant (n = 6). A crude plasma membrane fraction was prepared from the testes of each bird and an aliquot deriving from 10 mg of testicular tissue was used for binding assay. Specific binding of labeled LH or FSH was expressed as percentage of total radioactive hormone. Results showed significant (P < 0.05) age-related decreases in both FSH and LH receptor numbers. The highest FSH binding was found in young and middle-aged active males, with low binding in old inactive males. Testicular LH binding decreased during aging, with a sharp decrease in middle-aged males, which was similar to old males. Testosterone implants weakly stimulated FSH and LH binding in old males. Both LH and FSH binding decreased in photoregressed young males. However, testosterone implants stimulated increased LH binding, but did not affect FSH binding in young photoregressed males. These results provide evidence for separate regulation of testicular LH and FSH receptors, with testosterone stimulation of LH receptor, but not FSH receptor number in young males. However, during aging there appears to be a loss of this response, potentially because of the reduced efficacy of testosterone stimulation, thereby implying a diminished capacity for response with aging.     

Monozygotic and dizygotic twins' retrospective and current bereavement-related behaviors: an evolutionary perspective.

The present study compared bereavement responses of 325 monozygotic (MZ) and 176 dizygotic (DZ) adolescent and adult twins following the loss of their co-twins. A subset of twins completed the Grief Experience Inventory using a retrospective time frame, while a second subset completed it using a current time frame. It was hypothesized that MZ twins (in both retrospective and current groups) would report higher levels of grief-related behavior than DZ twins, consistent with Hamilton's (1964) concept of inclusive fitness. Discriminant function and profile analyses yielded supportive findings, but only for the retrospective MZ and DZ twin comparisons. Females in both groups expressed higher levels of bereavement-related behavior than males. Findings are discussed with reference to theoretical aspects of grief and mourning.     

Negative feedback regulation of gonadotropin secretion by androgens in fetal rhesus macaques

Previously we described sex differences in circulating gonadotropin concentrations (greater in females) in fetal rhesus macaques, and demonstrated that these sex differences relate, at least in part, to the negative feedback actions of testicular secretions. A fully functional gonadal-hypothalamic-pituitary feedback relationship is present as early as Day 100 of gestation in fetal males because castration at this time results in a dramatic increase (greater than 10-fold) in fetal luteinizing hormone (LH) concentrations. Although short-term (6-h) treatment of fetuses with testosterone (T) 3 wk after gonadectomy (GX) does not lower LH levels in males, it is completely effective in females. These data suggest that either T is not the primary testicular factor responsible for feedback suppression of LH in fetal males, or the hypothalamic-pituitary axis becomes insensitive to T after GX. To determine if immediate treatment with T after GX is effective in maintaining LH levels, we gonadectomized five fetal rhesus males on Days 98-104 of gestation and immediately implanted crystalline-T-containing intraabdominal Silastic capsules. An additional five fetuses were treated with the nonaromatizable androgen dihydrotestosterone (DHT). Umbilical arterial samples for hormone analysis were obtained prior to GX and again approximately 3 wk later. Serum from control males (n = 11) castrated in utero on Day 100 of gestation contained significantly greater concentrations of LH and follicle-stimulating hormone (FSH) 3 wk after the operation than before GX. Five sham-operated male fetuses did not have elevated levels of either LH or FSH in their serum on Day 120 of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)