Inhibins regulate peripheral regulatory T cell induction through modulation of dendritic cell function.

We have previously reported that the absence of inhibins results in impaired dendritic cell (DC) maturation and function, leading to decreased T cell activation and diminished delayed-type hypersensitivity responses. Here, we investigated the role of inhibins in peripheral regulatory T cell (Treg) induction in vitro and in vivo. Inhibin deficient (Inhα-/-) mice showed an increased percentage of peripherally induced Tregs in colonic lamina propria and mesenteric lymph nodes, compared to Inhα+/+ mice, which correlated with increased expression of PD-L1 in CD103+ and CD8α+ DCs. Lipopolysaccharide-stimulated bone marrow-derived and ex vivo spleen- and lymph node-purified CD11c+ Inhα-/- DCs induced higher Tregs in vitro. Moreover, in vivo anti-DEC205-ovalbumin (OVA) DC targeting of mice with adoptively transferred OVA-specific T cells showed enhanced induced peripheral Treg conversion in Inhα-/- mice. These data identify inhibins as key regulators of peripheral T cell tolerance.

Activin over-expression in the testis of mice lacking the inhibin α-subunit gene is associated with androgen deficiency and regression of the male reproductive tract.

Regionalised interaction of the activins, follistatin and inhibin was investigated in the male reproductive tract of mice lacking the inhibin α-subunit (Inha-/-). Serum and intratesticular activin B, although not activin A and follistatin, were increased in Inha-/- mice at 25 days of age, but all three proteins were elevated at 56 days. None of these proteins were altered within the epididymis and vas deferens at either age. At 25 days, histology of the epididymis and vas deferens was similar to wild-type. At 56 days, the testis contained extensive somatic cell tumours, leading to Leydig cell regression and testosterone deficiency. The epididymis and vas deferens showed epithelial regression and increased prominence of the interstitial stroma. Immunoregulatory and fibrotic gene expression in the epididymis and vas deferens were unchanged. Thus, absence of the inhibin α-subunit has marginal effects on activins in the epididymis and vas deferens, and regression of these tissues is associated with androgen deficiency.

The Testicular Hormones AMH, InhB, INSL3, and Testosterone Can Be Independently Deficient in Older Men.

BACKGROUND: Late-onset hypogonadism is symptomatically diverse and not fully explained by circulating testosterone level. The adult testes secrete four distinct hormones (testosterone, AMH, INSL3, and InhB) into the circulation. Testosterone and InhB have proven dynamic regulation, with limited information available for AMH and INSL3. During aging, there is cellular senescence, which may underlie the diversity of hypogonadism. This leads to the postulate that the relative levels (profile) of the four testicular hormones in older men are variable and cannot be evaluated by the measurement of one hormone. METHODS: 111 men aged 19-50 years and 98 men aged 70-90 years were examined. The circulating levels of the testicular hormones were measured using ELISAs, and the variation in the levels of hormones was analyzed by various correlative analyses. RESULTS: All four hormones were largely or totally independent. Some men were deficient in multiple hormones, but no man had multiple elevated hormones. The average hormonal levels were lower in older men, with diverse profiles of the four testicular hormones. Hence, some men had one or more hormones below the reference range, with testosterone the most conserved. Consequently, testosterone levels were not indicative of the complete state of the endocrine testes. CONCLUSIONS: The four hormones vary independently of each other, in younger and older men. This indicates that they are regulated dynamically rather than influenced by endocrine cell number. Older men exhibited diverse profiles of low levels of testicular hormones, suggesting that the testes age differently between men. Testosterone alone inadequately describes gonadal states.

Characterization of the mechanism of inhibin α-subunit gene in mouse anterior pituitary cells by RNA interference.

Inhibin, a member of the transforming growth factor-ß [TGF-ß] superfamily, is a suppressor of follicle-stimulating hormone [FSH] release through pituitary-gonadal negative feedback loop to regulate follicular development. In this study, Inhibin α-subunit [Inha] gene was knocked down successfully in mice primary anterior pituitary cells at both transcriptional and translational levels by RNAi-Ready pSIREN-RetroQ-ZsGreen Vector mediated recombinant pshRNA vectors. The results indicated that inhibin silencing significantly promoted apoptosis by up-regulating Caspase-3, Bax and Bcl-2 genes without affecting p53 both at transcriptional and translational levels. Furthermore, it markedly impaired the progression of G1 phase of cell cycle and decreased the amount of cells in S phase [as detected by flow cytometry]. Inhibin silencing resulted in significant up-regulation of mRNA and protein expressions of Gondotropin releasing hormone receptors [GnRHR] and down-regulated mRNA levels of ß-glycans with parellel change in the amount of its protein expression. Silencing of inhibin-a significantly increased [P<0.05] activin-ß concentration without affecting FSH and LH levels in anterior pituitary cells. These findings revealed that up regulation of GnRH receptors by silencing inhibin a-subunit gene might increase the concentration of activin-ß in the culture medium. Inhibin a silencing resulted in increased mRNA and protein expressions of inhibinß which may demonstrate that both inhibin subunits co-participate in the regulation of reproductive events in anterior pituitary cells. This study concludes that inhibin is a broad regulatory marker in anterior pituitary cells by regulating apoptosis, cellular progression and simultaneously by vital fluctuations in the hormonal signaling.

Action mechanism of inhibin α-subunit on the development of Sertoli cells and first wave of spermatogenesis in mice.

Inhibin is an important marker of Sertoli cell (SC) activity in animals with impaired spermatogenesis. However, the precise relationship between inhibin and SC activity is unknown. To investigate this relationship, we partially silenced both the transcription and translation of the gene for the α-subunit of inhibin, Inha, using recombinant pshRNA vectors developed with RNAi-Ready pSIREN-RetroQ-ZsGreen Vector (Clontech Laboratories, Mountain View, Calif). We found that Inha silencing suppresses the cell-cycle regulators Cyclin D1 and Cyclin E and up-regulates the cell-cycle inhibitor P21 (as detected by Western blot analysis), thereby increasing the number of SCs in the G1 phase of the cell cycle and decreasing the amount in the S-phase of the cell cycle (as detected by flow cytometry). Inha silencing also suppressed Pdgfa, Igf1, and Kitl mRNA levels and up-regulated Tgfbrs, Inhba, Inhbb, Cyp11a1, Dhh, and Tjp1 mRNA levels (as indicated by real-time polymerase chain reaction [PCR] analysis). These findings indicate that Inha has the potential to influence the availability of the ligand inhibin and its antagonist activin in the SC in an autocrine manner and inhibit the progression of SC from G1 to S. It may also participate in the development of the blood-testis barrier, Leydig cells, and spermatogenesis through its effect on Dhh, Tjp1, Kitl, and Pdgfa. Real-time PCR and Western blot analyses of Inha, Inhba, and Inhbb mRNA and Inha levels over time show that Inha plays an important role in the formation of round spermatid during the first wave of spermatogenesis in mice.

Defective gonadotropin-dependent ovarian folliculogenesis and granulosa cell gene expression in inhibin-deficient mice.

Inhibin-α knockout (Inha-/-) female mice develop sex cord-stromal ovarian cancer with complete penetrance and previous studies demonstrate that the pituitary gonadotropins (FSH and LH) are influential modifiers of granulosa cell tumor development and progression in inhibin-deficient females. Recent studies have demonstrated that Inha-/- ovarian follicles develop precociously to the early antral stage in prepubertal mice without any increase in serum FSH. These studies suggest that in the absence of inhibins, granulosa cells differentiate abnormally and thus at sexual maturity may undergo an abnormal response to gonadotropin signaling contributing to tumor development. To test this hypothesis, we stimulated immature wild-type and Inha-/- female mice with gonadotropin analogs prior to tumor formation and subsequently examined gonadotropin-induced ovarian follicle development as well as preovulatory and human chorionic gonadotropin-induced gene expression changes in granulosa cells. We find that at 3 wk of age, inhibin-deficient ovaries do not show further antral development or undergo cumulus expansion. In addition, there are widespread alterations in the transcriptome of gonadotropin-treated Inha-/- granulosa cells, with significant changes in genes involved in extracellular matrix and cell-cell communication. These data indicate the gonadotropins initiate an improper program of cell differentiation prior to tumor formation in the absence of inhibins.

A new FSHbeta mutation in a 29-year-old woman with primary amenorrhea and isolated FSH deficiency: functional characterization and ovarian response to human recombinant FSH.

CONTEXT: Mutations of the FSHbeta gene, causing in women isolated FSH deficiency and hypogonadism, are very rare and only a few have been described. OBJECTIVE: To describe the phenotype and response to recombinant human (rh) FSH of a female patient with a novel homozygous loss-of-function mutation of FSHbeta, and to characterize in vitro the molecular mechanisms responsible for the FSH inactivation. PATIENT: A 29-year-old woman with primary amenorrhea and impaired pubertal development associated with isolated FSH deficiency. METHODS AND RESULTS: Sequencing of the FSHbeta gene revealed a homozygous 1 bp (G) deletion at codon 79 (c.289delG) of exon 3 which produced a frameshift at codon 79 (A79fs108X) and a premature stop codon at codon 109. The wild-type and mutant FSHbeta cDNAs inserted into expression vector were cotransfected into Chinese hamster ovary cells with the alpha-subunit. Wild-type FSH was readily detectable in culture medium, whereas no mutant FSH was detectable by either immunoassay or in vitro bioassay. Mutant FSHbeta protein could not be detected in western blot. In response to a 15-day treatment with rhFSH, sonography revealed multifollicular development in the ovaries. Circulating levels of estradiol and inhibin B were dramatically increased, whereas anti-Mullerian hormone decreased. Serum LH first decreased and then increased, inducing multiovulation associated with supraphysiologic progesterone and inhibin A levels. CONCLUSION: A novel FSHbeta mutation was detected in a hypogonadal woman. rhFSH was effective in ovulation induction in the patient but with signs of ovarian hyperstimulation. The high pretreatment LH levels could contribute to this excessive ovarian response to rhFSH.

Loss of inhibin alpha uncouples oocyte-granulosa cell dynamics and disrupts postnatal folliculogenesis.

Targeted disruption of the inhibin alpha gene (Inha(-)(/)(-)) in mice results in an ovarian phenotype of granulosa cell tumors that renders the animals infertile. Little is known about the reproductive defects prior to tumor development. Here, we report novel data on early follicle dynamics in Inha(-)(/)(-) mice, which demonstrate that inhibin alpha has important consequences upon follicle development. Morphological changes in both germ and somatic cells were evident in postnatal day 12 ovaries, with Inha(-/-) mice exhibiting numerous multilayered follicles that were far more advanced than those observed in age-matched controls. These changes were accompanied by alterations in follicle dynamics such that Inha(-/-) ovaries had fewer follicles in the resting pool and more committed in the growth phase. Absence of inhibin alpha resulted in advanced follicular maturation as marked by premature loss of anti-Müllerian hormone (AMH) in secondary follicles. Additionally, gene expression analysis revealed changes in factors known to be vital for oocyte and follicle development. Together, these data provide key evidence to suggest that regulation of the inhibin/activin system is essential for early folliculogenesis in the prepubertal mouse ovary.

Luteinizing hormone promotes gonadal tumorigenesis in inhibin-deficient mice.

The inhibins are secreted alpha:beta heterodimers of the TGF-beta superfamily that are mainly synthesized in Sertoli cells and granulosa cells, and are critical regulators of testicular and ovarian development and function. Mice homozygous for a targeted deletion of the inhibin alpha subunit gene (Inha(-/-)) develop sex cord-stromal tumors in a gonadotropin-dependent manner. Here, we determine the contribution of LH to gonadal tumorigenesis by generating mice deficient in both inhibins and LH. Inha(-/-)Lhb(-/-) mice have increased survival and delayed tumor progression, and these observations correlate with lower serum FSH and estradiol levels compared to Inha(-/-) controls. Double mutant testicular tumors demonstrate decreased expression of cyclin D2, while double mutant ovarian tumors have elevated expression of p15(INK4b) and trend toward higher levels of p27(Kip1). We conclude that LH is not required for tumor formation in the absence of inhibins but promotes tumor progression, likely through alterations in serum hormone levels and cell cycle regulators.

Effects of downregulation of inhibin alpha gene expression on apoptosis and proliferation of goose granulosa cells.

Inhibin alpha is one of the candidate genes that control the ovulation in poultry. To study the genetic effects of inhibin alpha on apoptosis and proliferation of goose granulosa cells cultured in vitro, two RNA interference (RNAi) expression vectors, psiRNA-INH alpha 1 and psiRNA-INH alpha 2, were constructed to knock down inhibin alpha gene expression. After 48 h of transfection, the efficiency of these two RNAi expression vectors was examined by fluorescence microscopy. Meanwhile, inhibin protein expression levels, apoptosis indexes (AI) and proliferation indexes (PI) of granulosa cells were analyzed by flow cytometry. In addition, the supernatants were collected to assay the concentrations of estrogen (E2) and progesterone (P) by radioimmunoassay. The results showed that the expression level of inhibin alpha in the RNAi group were decreased 30%-40% than those in the control groups (P < 0.05) and the apoptosis indexes and proliferation indexes in the RNAi groups were significantly higher than those in the control groups (P < 0.05). However, the E2 concentrations in the RNAi groups were lower than those in the control groups (P < 0.05). These results indicate that inhibin alpha has antagonistic effect on granulosa cell apoptosis.

Prevention of cachexia-like syndrome development and reduction of tumor progression in inhibin-deficient mice following administration of a chimeric activin receptor type II-murine Fc protein.

Inhibin is a secreted tumor suppressor, and inhibin alpha null mice develop gonadal sex cord-stromal tumors with 100% penetrance at an early age. Inhibin-deficient mice die of a severe wasting syndrome due to increased activin signaling through activin receptor type II. The current study was designed to assess the in vivo effects of an activin antagonist, a chimeric activin receptor type II fused to the Fc region of a murine IgG2a (ActRII-mFc), administered transiently to the inhibin-deficient mice. Results showed that the severe weight loss was prevented in the ActRII-mFc-treated mice, FSH levels were reduced, and an extended life span was observed for these mice compared with phosphate-buffered saline-treated controls. Although ActRII-mFc treatment did not seem to prevent the formation of gonadal tumors, tumors were smaller in the majority of experimentally treated mice and were characterized by the presence of variable numbers and sizes of cysts in contrast to the solid hemorrhagic tumors that typically developed in the controls. Moreover, the ActRII-mFc-treated mice were less anemic, and their livers and stomachs were histologically normal. In summary, this study demonstrated that in vivo administration of the activin antagonist, ActRII-mFc, not only prevents the cachexia-like symptoms in the inhibin-deficient mouse model, but also reduces tumor progression. These results support an essential role of activins in the cachexia-like syndrome development and implicate activins as growth-promoting factors in gonadal tumor progression. The current findings have potential implications in the design of new drugs or strategies for the treatment of ovarian and testicular tumors and other conditions where ligands signal through ActRII.

Follicular arrest in polycystic ovary syndrome is associated with deficient inhibin A and B biosynthesis.

CONTEXT: Previous studies suggest that inhibin subunit expression is decreased in granulosa cells of women with polycystic ovary syndrome (PCOS). OBJECTIVE: The objective of this study was to test the hypothesis that inhibin A and inhibin B protein concentrations are also decreased in PCOS follicles. DESIGN: The design was a parallel study. SETTING: The study was performed at an in vitro fertilization suite. PARTICIPANTS: We studied women with regular cycles (n = 36) and women with PCOS (n = 8). INTERVENTIONS: Follicular fluid was aspirated from the follicles of women with PCOS (n = 14 follicles) and from women with regular cycles at various times during the follicular phase (n = 50 follicles). MAIN OUTCOME MEASURE: Inhibin A and B concentrations from PCOS follicles were compared with those in size-matched follicles, dominant follicles (> or = 10 mm), and subordinate follicles from regularly cycling women. RESULTS: Inhibin A (220 +/- 38 vs. 400 +/- 72 IU/ml; P < 0.05) and inhibin B (75.4 +/- 10.4 vs. 139 +/- 26 ng/ml; P < 0.05) concentrations were lower in the follicular fluid of PCOS follicles compared with those of size-matched follicles from regularly cycling women. Inhibin A was also lower in the follicular fluid of PCOS compared with subordinate follicles from normal women (577 +/- 166 IU/ml; P < 0.05). Inhibin A concentrations increased with increasing follicle size, resulting in significantly higher follicular fluid concentrations in dominant follicles from normal women compared with PCOS follicles (2298 +/- 228 IU/ml; P < 0.05). CONCLUSIONS: These data demonstrate that inhibin A and inhibin B concentrations are significantly reduced in the follicular fluid of women with PCOS compared with those in the follicular fluid of size-matched follicles from normal women, consistent with the decreased inhibin subunit mRNA expression in previous studies. These findings point to the potential importance of inhibins in normal follicle development and suggest that inhibin deficiency may play a role in the follicle arrest associated with PCOS.

Sequestration of connexin43 in the early endosomes: an early event of Leydig cell tumor progression.

Connexins form gap junction channels that allow intercellular communication between neighboring cells. Compelling evidence has revealed that Cx are tumor-suppressor genes and reduced Cx expression has been related with uncontrolled cell growth in tumors and transformed cells. In the present study, we addressed Cx transcriptional and posttranscriptional regulations during the earlier stage of testicular tumors confined to Leydig cells in a transgenic mice model. In situ hybridization indicated that connexin43 (Cx43) mRNA was highly expressed either at early tumorogenesis (3 m) characterized by intense proliferation of Leydig cells, or at advanced tumorogenesis (6-7 m) when tumor cells completely invaded the testis. In contrast, Cx43 protein analyzed by Western blotting or classic immunohistochemical analyses was present at the beginning of tumor progression, but was dramatically reduced as tumor advanced. Application of high-resolution deconvolution microscopy to testis sections demonstrates that cells that proliferate exhibited an aberrant cytoplasmic Cx43 localization, in contrast to the expected plasma membrane Cx43 localization in normal Leydig cells. Dual immunofluorescence labeling with specific markers of cellular compartments shows that cytoplasmic Cx43 signal was mainly sequestered within early endosomes. Altogether, this study provides the first evidence that impaired Cx43 trafficking in endosomes is an early event associated with uncontrolled cell proliferation that could serve as a neoplastic marker.

Expression profiling analyses of gonadotropin responses and tumor development in the absence of inhibins.

Transgenic mice with engineered disruptions in bidirectional endocrine signaling between the pituitary and gonad have shed light on the specific effects of the loss of function of gonadotropins and inhibins. These models are valuable tools for studying ovarian biology because they phenocopy specific pathological states and have variations in ovarian tissue composition that allow us to identify genes expressed in specific cell types. We have used emerging mRNA expression profiling technologies to gain a more comprehensive view of genes that are expressed in the mammalian ovary and adrenal gland in the FSHbeta and inhibin alpha knockout mouse models. Oligonucleotide array hybridization experiments using Affymetrix GeneChip technology and NIA 15K murine cDNA microarray studies identified hundreds of transcripts differentially expressed compared with wild type, over 30 of which were selected for further characterization by Northern blot analyses. Additionally, we performed in situ hybridization studies to localize 10 mRNAs, melanocyte-specific gene 1, amino acid transporter SN2, overexpressed and amplified in teratocarcinoma (Bcat1), Forkhead box protein FOXO1, 24p3, vascular cell adhesion molecule, epiregulin, Bcl2-like10, PC3B, and retinoblastoma binding protein 7. These 10 genes have expression patterns and postulated functions suggesting that they mediate important processes in the physiology and pathology of ovarian and adrenal tissue.

Follistatin is a modulator of gonadal tumor progression and the activin-induced wasting syndrome in inhibin-deficient mice.

Inhibins and activins are dimeric proteins belonging to the transforming growth factor-beta superfamily. Follistatin is an activin-binding protein that antagonizes the function of activin via binding to its beta-subunits. Previously, we demonstrated that mice deficient in inhibin develop ovarian and testicular sex cord-stromal tumors of granulosa and Sertoli cell origin, with 100% penetrance as early as 4 weeks of age. Overproduction of activins in the serum directly causes a cachexia-like wasting syndrome that results in lethality of these mice at an early stage after the onset of the tumors. In an independent set of studies, overexpression of mouse follistatin using the mouse metallothionein I promoter in transgenic mice led to gonadal defects and eventual infertility, primarily due to local effects of follistatin in these tissues. Activin has a positive growth effect on gonadal tumor cells in culture and directly causes the cancer cachexia-like syndrome in inhibin-deficient mice via interaction with activin receptor type IIA in livers and stomachs. We therefore hypothesized that an activin antagonist such as follistatin can act as a physiological modifier, either locally or via the serum, to block the activin-mediated cancer cachexia-like syndrome in inhibin-deficient mice and/or slow the progression of gonadal cancers in these mice. To test this hypothesis, we generated mice that are homozygous mutant for the inhibin alpha null allele (i.e. inham1/inham1) and carry the mouse metallothionein I follistatin (MT-FS) transgene. Our results show that gonadal tumors that are histologically similar in most, but not all, cases to the tumors in inhibin-deficient mice develop in these inham1/inham1, MT-FS+ mice. However, inham1/inham1, MT-FS+ mice exhibit a less severe wasting syndrome, lower serum activin levels, and a statistically significant prolonged survival in a number of cases compared with mice deficient in inhibin alone. Thus, follistatin can act as a modulator of tumor growth and the activin-induced cancer cachexia-like syndrome in inhibin-deficient mice.

Activin A promotes progenitor differentiation into photoreceptors in rodent retina.

Activins are TGF beta-like proteins that were first discovered for their actions on the reproductive system, but have subsequently been shown to play a role in a variety of developmental processes. Previous studies have demonstrated that activins and their receptors are present in the developing retina, as well as other regions of the embryonic nervous system. We used both in vitro and in vivo approaches to test for functions of activin during retinal development. We found that activin A treatment of embryonic day 18 rat retinal cultures causes the progenitor cells in the cultures to exit the cell cycle and differentiate into rod photoreceptors. This effect is dose-dependent and the promotion of rod photoreceptor differentiation is specific, since the other primary retinal neurons generated in these cultures, the C1+ amacrine cells, are not affected by activin A treatment. Mice with homozygous deletion of the activin betaA gene show a specific decrease in the number of rod photoreceptors compared to wild-type or heterozygous littermates. These data demonstrate that activin A is an important regulator of photoreceptor differentiation in the developing retina.

A transiçäo da perimenopausa / The perimenopausal transition

Os objetivos deste artigo säo: 1- Definir idade de início e duraçäo da transiçäo da perimenopausa. 2- Descrever as alteraçöes hormonais, lipídicas e ósseas que ocorrem durante a transiçäo da perimenopausa. 3- Atentar para os principais requisitos de cuidados preventivos com a saúde no período da vida correspondente à perimenopausa.

Defective whisker follicles and altered brainstem patterns in activin and follistatin knockout mice.

Whisker pad innervation and whisker-specific pattern formation were examined in mice lacking the gene for activin betaA or for follistatin. Both strains of mice die within 24 h after birth. A normal array of whisker follicles is present in the snout of either phenotype. However, activin betaA-deficient mice lack whiskers, and in follistatin-deficient mice the whiskers are thin and curled. We examined the effects of aberrant, albeit innervated, follicles on the formation of whisker-specific patterns (barrelettes) in the trigeminal brainstem. Activin betaA knockout mice lack barrelettes, although the trigeminal afferent topography is not compromised. Physiological recordings suggest that trigeminal ganglion cells in these mice are less responsive to stimulation of whisker follicles. Barrelettes in follistatin-deficient mice are not as well developed as in controls, but can be discerned in some cases. These results are consistent with the notion that formation of barrelettes depends on neural activity initiated by the whiskers.

Men homozygous for an inactivating mutation of the follicle-stimulating hormone (FSH) receptor gene present variable suppression of spermatogenesis and fertility.

Gonadal function is controlled by the two pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). While LH mainly regulates gonadal steroidogenesis, FSH is considered essential for folliculogenesis in the female and spermatogenesis in the male. We recently discovered that an inactivating point mutation in the FSH receptor (R) gene causes a recessively inherited form of hypergonadotropic ovarian failure in homozygous females. This 566C-->T mutation, predicting an alanine to valine substitution, is located in exon 7 of the FSHR gene, in the region encoding the extracellular domain of the receptor molecule. Functional testing showed a clear-cut reduction in ligand binding and signal transduction by the mutated receptor. Hence, lack of FSH function is incompatible with ovarian follicular maturation and female fertility. In the male, FSH is generally considered essential for the pubertal initiation of spermatogenesis and maintenance of quantitatively normal sperm production in adults. We report here the first characterization of males homozygous for an inactivating FSHR mutation. They have variable degrees of spermatogenic failure, but, surprisingly, do not show azoospermia or absolute infertility. These results question the essential role of FSH for the initiation of spermatogenesis, and demonstrate that FSH is more important for female than for male fertility.

Gonadotropins are essential modifier factors for gonadal tumor development in inhibin-deficient mice.

We previously demonstrated that mice deficient in inhibin develop gonadal sex cord-stromal tumors with nearly 100% penetrance. These ovarian and testicular tumors develop as early as 4 weeks of age and eventually cause cachexia-like symptoms and death in the inhibin-deficient mice. Gonadectomized inhibin-deficient mice initially do not develop this wasting syndrome, but eventually will develop adrenal cortical tumors with similar penetrance. These studies have demonstrated that inhibin is a secreted type of tumor suppressor in the gonads and adrenal glands. Gonadotropins are implicated to influence gonadal tumor development in humans as well as experimental animals, and in inhibin-deficient mice, serum FSH levels are elevated. To determine whether gonadotropins influence the development and/or progression of the tumors in the inhibin-deficient mice, we took advantage of a naturally occurring mutant mouse, hypogonadal (hpg); hpg/hpg mice lack a functional GnRH gene and, therefore, have suppressed FSH and LH levels. Heterozygous hpg/+mice were crossed to heterozygous inhibin mutant mice to generate compound homozygous mutant mice that lack both inhibin and GnRH. These compound homozygous mutant mice do not develop a wasting syndrome, do not exhibit gonadal or adrenal tumors, and can survive for more than 1 yr. These results demonstrate that gonadotropins are essential modifier factors for tumor development in inhibin-deficient mice.