Inhibin immunohistochemical staining: a practical approach for the surgical pathologist in the diagnoses of ovarian sex cord-stromal tumors

Immunohistochemical markers of prognosis in adult granulosa cell tumors of the ovary - a review

BACKGROUND

Granulosa cell tumors (GCT) are rare malignant ovarian tumors. The two subtypes, adult and juvenile granulosa cell tumors, differ in clinical and molecular characteristics. GCT are low-malignant tumors and are generally associated with favorable prognosis. However, relapses are common even years and decades after diagnosis. Prognostic and predictive factors are difficult to assess in this rare tumor entity. The purpose of this review is to provide a comprehensive overview of the current state of knowledge on prognostic markers of GCT to identify patients with a high risk of recurrence.

METHODS

Systematic research for adult ovarian granulosa cell tumors and prognosis revealed n = 409 English full text results from 1965 to 2021. Of these articles, n = 35 were considered for this review after title and abstract screening and topic-specific matching. A specific search for pathologic markers with prognostic relevance for GCT identified n = 19 articles that were added to this review.

RESULTS

FOXL2 mutation and FOXL2 mRNA were inverse and immunohistochemical (IHC) expression of CD56, GATA-4 and SMAD3 was associated with reduced prognosis. IHC analysis of estrogen receptor, Anti-Mullerian hormone (AMH) and inhibin was not associated with prognosis for GCT. Analyses of mitotic rate, Ki-67, p53, β-catenin and HER2 revealed inconsistent results.

Inhibin Alpha Expression in Human Tumors: A Tissue Microarray Study on 12,212 Tumors

As a result of its expression in corresponding normal cell types, inhibin alpha (INHA) is used as an immunohistochemical marker for adrenocortical neoplasms and testicular or ovarian sex cord stromal tumors. However, other tumors can also express INHA. To comprehensively determine INHA expression in cancer, a tissue microarray containing 15,012 samples from 134 different tumor types and subtypes was analyzed by immunohistochemistry. INHA positivity was found in 72 of 134 tumor categories, including 26 categories with ≥1 strongly positive case. A moderate to strong INHA positivity was found in 100% of 37 granulosa cell tumors of the ovary, 100% of 43 other sex cord stromal tumors of the ovary/testis, 100% of 31 granular cell tumors, 78.5% of 28 adenomas, 44% of 25 carcinomas of the adrenal cortex, and 46.7% of 15 pancreatic acinar cell carcinomas. At least a weak INHA positivity was seen in <33% of cases of 46 additional tumor entities. In summary, these data support the use of INHA antibodies for detecting sex cord stromal tumors, granular cell tumors, and adrenocortical neoplasms. Since INHA can also be found in other tumor entities, INHA immunohistochemistry should only be considered as a part of any panel for the distinction of tumor entities.

Targeted Genomic Profiling of Female Adnexal Tumors of Probable Wolffian Origin (FATWO)

Female adnexal tumor of probable Wolffian origin (FATWO) is a rare gynecologic neoplasm of low-malignant potential presumed to be derived from mesonephric remnants in the upper female genital tract. Similarly, mesonephric remnants in the lower female genital tract are thought to be the origin for mesonephric carcinoma. Although the molecular alterations in mesonephric carcinoma have been recently reported, the pathogenesis of and molecular alterations in FATWO are not well understood. The aims of this study were to examine the molecular alterations in FATWO and to establish whether these neoplasms are molecularly similar to mesonephric carcinoma. Eight FATWOs underwent massively parallel sequencing to detect single nucleotide variations, copy number variations, and structural variants by surveying exonic DNA sequences of 300 cancer genes and 113 introns across 35 genes. Good quality DNA was isolated from 7 of 8 cases. Novel KMT2D variants (1 frameshift, 3 missense) were identified in 4 of 7 cases (57%), but were variants of uncertain biologic significance. STK11 mutations (both frameshift) were identified in 2 of 7 cases (29%); one of these was in a patient with a known history of Peutz-Jeghers syndrome. A mutation in the chromatin remodeling gene ARID1B was identified in 1 of 7 cases (14%). No cases harbored KRAS, NRAS, TP53, PIK3CA, PTEN, or DICER1 mutations. There were relatively low numbers of copy number variations, and no recurrent copy number variations were identified. One case demonstrated moderate copy gain of CCND1. No structural variants were identified. In summary, FATWO is characterized molecularly by the absence of KRAS/NRAS mutations (characteristic of mesonephric carcinoma), absence of DICER1 mutations (characteristic of Sertoli-Leydig cell tumor) and frequent KMT2D mutations of unknown biologic significance. FATWOs exhibit a limited number of molecular aberrations that are significantly different from those reported in tumors in the differential diagnosis, and our results question the relationship of mesonephric carcinoma with FATWO. Disease-defining molecular alterations for FATWO have yet to be discovered.

Differentiating Intrarenal Ectopic Adrenal Tissue From Renal Cell Carcinoma in the Kidney

BACKGROUND

Adrenal rest (AR) is the presence of ectopic adrenal cortical tissue, often identified incidentally during autopsy (20% of postmortem examination). In the kidney, AR can be found in 6% of the general population. Ectopic adrenal tissue is of no functional significance but may in some cases, pose a diagnostic challenge for the pathologist, especially in the context of renal clear cell renal cell carcinoma (RCC) and small needle biopsies.

AIM

To investigate the utility of immunohistochemical stains in distinguishing AR from RCC.

METHODS

Archival cases of AR, in our institution, were reviewed and compared with a cohort of RCC cases using a panel of immunohistochemical stains, including PAX2, PAX8, calretinin, and inhibin.

RESULTS

Nine of 10 (90%) cases of AR showed positive staining for inhibin and negative staining for calretinin, PAX2 and PAX8. One AR case was positive for PAX2 and PAX8 in addition to inhibin. All (100%) RCC cases were positive for PAX2 and PAX8, but negative for inhibin and calretinin.

CONCLUSIONS

A panel of PAX2, PAX8 and inhibin may be useful markers for distinguishing AR from RCC. Calretinin was noncontributory in our study.

Ovarian leydig cell hyperplasia: an unusual case of virilization in a postmenopausal woman

Objective. To report an unusual case of ovarian Leydig cell hyperplasia resulting in virilization in a postmenopausal woman. Methods. Patient's medical history and pertinent literature were reviewed. Results. A 64-year-old woman presented with virilization with worsening hirsutism, deepening of her voice, male musculature, and male pattern alopecia. Her pertinent past medical history included type 1 diabetes, hyperlipidemia, and hypertension. Her pertinent past surgical history included hysterectomy due to fibroids. On further work-up, her serum total testosterone was 506 ng/dL (nl range: 2-45) and free testosterone was 40 pg/mL (nl range: 0.1-6.4). After ruling out adrenal causes, the patient underwent an empiric bilateral oophorectomy that showed Leydig cell hyperplasia on pathology. Six weeks postoperatively, serum testosterone was undetectable with significant clinical improvement. Conclusion. Postmenopausal hyperandrogenism can be the result of numerous etiologies ranging from normal physiologic changes to ovarian or rarely adrenal tumors. Our patient was found to have Leydig cell hyperplasia of her ovaries, a rarely reported cause of virilization.

Successful term pregnancies after laparoscopic excision of poorly differentiated Sertoli-Leydig cell tumor of the ovary

Ovarian Sertoli-Leydig cell tumors are rare sex cord-stromal tumors, accounting for less than 1% of ovarian tumors. Majority of these tumors are benign and unilateral, only 3-5% are bilateral. These patients present with clinical features of virilization due to excessive secretion of testosterone from the tumor, however 50% may have no endocrine symptoms. We report a case of poorly differentiated Sertoli-Leydig cell tumour in a woman diagnosed during routine investigation of infertility. She had two spontaneous successful pregnancies after tumor excision laparoscopically.

Sex cord stromal tumors of the ovary in children: a clinicopathological report from the Italian TREP project

BACKGROUND

Ovarian sex-cord stromal tumors (SCST) are rare in childhood and include a variety of neoplasms with different clinical features and biologic behavior. Aim of the analysis was to report the clinical findings and treatment results of a series of patients with SCST of the ovary, registered in a multi-institutional Italian network on rare tumors in children and adolescent between 2000 and 2009.

METHODS

Data on 23 patients, 5-176 months old, from 13 Centers were reviewed. All patients were grouped on the basis of the results of the first surgical approach, according to the Children Oncology Group staging system. A cisplatin based chemotherapy was recommended in patients with a localized disease, who had undergone an incomplete excision/initial biopsy, and in case of metastatic spread.

RESULTS

A frequent symptom was abdominal pain; 9/23 cases had signs of hormonal secretion and two patients were hospitalized for acute pain following ovarian torsion. Twelve patients had a Juvenile-Granulosa Cell tumor, six a Sertoli-Leydig Cell tumor, three a Fibrothecoma, and two a Sclerosing-Stromal tumor. Twenty-one patients maintained the complete remission (follow-up: 9-91 months), 2 with a ST II Sertoli-Leydig Cell tumor relapsed and one of them died. Immonohistochemical studies could be done in 10 cases.

CONCLUSIONS

Completeness of resection and histology were important prognostic factors; in our series the Sertoli-Leydig Cell tumor was the most aggressive variety. Hormonal signs (precocious puberty, telarca, menarche) were common in younger patients and led to an early diagnosis. Cisplatin based chemotherapy seemed to be effective for locally advanced tumors.

[The role of the pathologist in the diagnosis of metastases from urological malignancies]

Metastases are sometimes the first revelation of urologic cancers. The role of the pathologist in case metastatic disease of unknown origin is to affirm the malignant character of the lesion; provide histological information for possible origins; and to give histological therapeutic arguments. In most of the cases the histological analysis based on cellular morphology is sufficient to suspect a particular origin. In case of poor differentiated carcinoma in addition to the histological analysis, the immunohistochemical study allows the detection of various specific antigens. In this review we approach the various morphological criteria and the interest of the various antibodies to confirm the urologic origin of a metastasis.

Biphasic malignant testicular sex cord-stromal tumor in a cotton-top tamarin (Saguinus oedipus) with review of the literature

A 20-year old male cotton-top tamarin (Saguinus oedipus) was presented with unilateral enlargement of an intrascrotal testicle. Fine-needle aspiration cytology demonstrated a neoplastic population with Call-Exner-like bodies and features of malignancy. The animal was castrated, and histologic examination revealed a biphasic sex cord-stromal tumor, with one region resembling Sertoli-cell tumor and one region resembling granulosa-cell tumor, with extensive microfollicular pattern and many Call-Exner bodies. Eight months after castration, the animal was euthanized on discovery of a caudal abdominal mass that displaced organs, was highly infiltrative, and extended into the paravertebral musculature with lysis of vertebral bone. Metastases to lymph node and lung were also present. Histologic examination of the abdominal tumor showed multifocal formation of Call-Exner bodies in an otherwise highly dedifferentiated population. Positive immunolabeling for alpha inhibin confirmed the sex cord-stromal origin of the abdominal and paravertebral tumor masses. This case has similarities to malignant testicular granulosa-cell tumor of humans.

Molecular genetic evidence supporting the neoplastic nature of the Leydig cell component of ovarian Sertoli-Leydig cell tumors

Sertoli-Leydig cell tumors (SLCT) comprise less than 1% of ovarian tumors. The nature of the Leydig cells has been a subject of controversy and it is unclear whether they are clonally related to the neoplasm or instead proliferate as a non-neoplastic response to the Sertoli-cell component. Twelve ovarian SLCT were identified and hematoxylin and eosin and unstained sections were prepared from formalin-fixed, paraffin-embedded tissue blocks. Tissue samples were microdissected from normal tissue, the Sertoli cell component, and the Leydig cell tumor component using the laser capture microdissection method. If present, tissue was also obtained from any heterologous component. Genomic DNA was extracted from the samples and polymerase chain reaction was used to amplify polymorphic sites at 5 loci: D16S402, TP53, IFNA, D17S855, and D11S1318. X-chromosome inactivation (HUMARA) analysis was also performed. LOH and/or nonrandom X-chromosome inactivation was observed in at least 1 of the 6 amplified loci in the Leydig cell component of 10 of the 12 tumors. LOH and nonrandom X-chromosome inactivation patterns of the Sertoli cell component and Leydig cell component were compared. Concordant allelic loss and/or matching X-chromosome inactivation patterns were observed in 8 (67%) of the 12 tumors. In 7 of these tumors similar LOH or X-chromosome inactivation was observed at 1 site. In 1 tumor similar LOH and/or X-chromosome inactivation was observed at 2 sites. Three tumors had heterologous components. The heterologous components similarly shared LOH/X-chromosome inactivation with the Sertoli cell components at 1 site in 1 case and 2 sites in 2 cases. These data suggest that, at least in some cases, the Leydig cell component of SLCT is neoplastic rather than reactive in nature, and shares a common clonal origin with the coexisting Sertoli cell component. Similarly, the heterologous components, when present, appear to share clonal origin with the Sertoli cell components.

CD10 Expression in Pure Stromal and Sex Cord-Stromal Tumors of the Ovary

CD10 has been recently advocated as a good immunohistochemical marker for endometrial stromal tumors. Metastatic endometrial stromal tumors to the ovary and primary endometrioid stromal sarcomas may show overlapping histological features with pure stromal and sex cord-stromal tumors (SCSTs). We investigated CD10 expression in a large series of pure stromal and SCSTs of the ovary to ascertain whether CD10 may aid in this differential diagnosis. Archival material from 11 fibromas, 10 thecomas, 10 sclerosing stromal tumors (SSTs), 10 adult granulosa cell tumors (AGCTs), 4 luteinized AGCTs, 9 juvenile granulosa cell tumors (JGCTs), 9 Sertoli cell tumors, 9 Sertoli-Leydig cell tumors, 11 sex cord tumors with annular tubules, 10 steroid cell tumors (StCTs), and 8 fibrosarcomas of the ovary were immunostained for CD10. The percentage of cells stained (<5%, 5%-39%, 40%-75%, and >75%) and intensity of staining (1+, 2+, 3+) were evaluated. CD10 was expressed in 7 of 10 thecomas (4 with 5%-75% and mostly 1+), 9 of 10 SSTs (7 with 5%-39% + cells, mostly 1+), 9 of 10 AGCTs (<5%-39%, four 1+, five 2+), 1 of 4 luteinized AGCTs (<5% and 1+), 8 of 9 JGCTs (mostly <5% to 39% and +1), 4 of 9 Sertoli cell tumors (either focal or >75% with variable intensity), 4 of 9 Sertoli-Leydig cell tumors (mostly <10% with variable staining), with the Leydig cells being positive in only 1 tumor (1+ and <5%), and 7 of 10 StCTs (4 tumors with more than 75% + cells, from 1+ to 3+). All fibromas, all but 1 fibrosarcoma (<5% and 1+), and all sex cord tumors with annular tubules were CD10 negative. CD10 expression was frequently seen in StCTs, SSTs, and thecomas of the ovary, although the latter 2 categories usually showed only faint immunoreactivity. In conclusion the frequency and intensity of CD10 immunoreactivity in pure stromal and sex cord-stromal ovarian tumors are low and contrast with the typical strong and diffuse immunostaining seen in endometrial stromal tumors; however, faint CD10 positivity is consistent with the diagnosis of ovarian SCST. Steroid cell tumors are often positive for CD10, but these tumors do not pose problems in differential diagnosis with endometrial stromal tumors. CD10 may play a useful role in aiding the differential between endometrial stromal tumors in the ovary and SCST and stromal tumors.

Ovarian spindle cell lesions: a review with emphasis on recent developments and differential diagnosis

Ovarian lesions composed of spindle cells comprise a heterogeneous group; most are neoplastic but several non-neoplastic conditions are also composed of spindle cells. This review discusses the main differential diagnoses of an ovarian spindle cell lesion, especially concentrating on the recent literature. The majority of ovarian spindle cell lesions fall into the broad category of fibromatous neoplasms whereas others in the sex cord-stromal group may also be composed of spindle cells, including thecomas, granulosa, and Sertoli-Leydig cell tumors and rarer neoplasms, such as sclerosing stromal tumor and signet-ring stromal tumor. In the recent past there have been several major contributions on various aspects of ovarian spindle cell lesions, including cellular and mitotically active cellular fibromatous lesions, smooth muscle neoplasms, and metastatic gastrointestinal stromal tumors. Other mesenchymal or epithelial tumors and mixed epithelial and mesenchymal neoplasms may also enter into the differential diagnosis of an ovarian spindle cell lesion. Several non-neoplastic lesions may be composed of spindle cells, including massive edema, ovarian fibromatosis, stromal hyperplasia, and stromal hyperthecosis. Morphology remains the mainstay in diagnosis but immunohistochemistry may be invaluable in certain circumstances, one example being the identification of a metastatic gastrointestinal stromal tumor within the ovary.

Inhibin as a diagnostic marker for ovarian cancer

The inhibins are a family of growth factors comprised of several different species that are secreted in the female principally from the ovarian follicle. The inhibins perform best as markers of ovarian cancer when measured collectively (total inhibin) by immunoassays targeted to common epitopes. After menopause with the depletion of ovarian follicles, the circulating level of total inhibin becomes undetectable. In contrast, serum total inhibin levels are elevated in women with ovarian cancer, in particular those with granulosa cell tumours and those with the mucinous subtype of epithelial carcinoma. Investigations into the clinical utility of inhibin to detect ovarian cancer have shown that it complements CA125, an established marker of epithelial ovarian cancer, in that each performs best in detecting different subtypes of ovarian cancer. In some published studies, the two markers together have detected up to 95% of ovarian cancers with 95% specificity.

Immunohistochemical and ultrastructural analysis of a poorly differentiated pediatric age Sertoli–Leydig cell tumor

Ovarian Sertoli-Leydig cell tumors (SLCT) are rare in young women. They are divided into six categories based on the degree of differentiation and the presence of heterologous elements. Less than 15% of these tumors are poorly differentiated. A 14-year-old obese African-American girl presented with amenorrhea, progressive abdominal pain, and increasing abdominal girth. Pelvic CT revealed a 10 x 9 x 9 cm right adnexal mass which was resected successfully. The gross appearance was dark tan and red with central hemorrhage and necrosis. Microscopically, this was poorly differentiated with compact aggregates of moderate size oval to elongated cells separated by zones of edematous stroma containing scattered spindle shape cells. Areas of ill-formed tubules and primitive cords were present. Clusters of Leydig cells were observed. The oval and spindle cells showed multiple mitoses and were diffusely positive for inhibin and patchy but strong positivity for calretinin. Both preoperative and postoperative studies revealed no metastases. Serum alpha-fetal protein (AFP), androgen, and dihydroepiandrosterone sulfate (DHEA-S) were elevated.

The diagnosis of malignancy in effusion cytology: a pattern recognition approach

This review presents a pattern recognition approach for the diagnosis of malignant effusions. The cytomorphologic features of reactive mesothelial proliferation, mesothelioma and metastatic carcinoma are presented. In addition, the role of ancillary studies in challenging cases and the importance of integrating clinical findings are stressed. An algorithmic approach to the workup of serous effusions as well as pitfalls for false-positive diagnosis are discussed.

The utility of calretinin, inhibin, and WT1 immunohistochemical staining in the differential diagnosis of ovarian tumors

Calretinin has been proposed as a novel marker of ovarian sex cord-stromal tumors (SCST); this study aims to determine whether calretinin can complement or supplant the established utility of inhibin in the differential diagnosis of SCST. WT1 has been shown to be expressed in ovarian serous, but not mucinous neoplasms; its expression in a variety of ovarian tumors is also examined. Formalin-fixed, paraffin-embedded archival tissues from 111 primary ovarian tumors were analyzed with commercially available antibodies using semi-automated immunohistochemistry. Results were graded on a 4-tiered scale with staining of more than 0 but less than 5% of cells considered focal. Of 27 SCST, 56% were calretinin and 56% inhibin positive overall; 90% of granulosa cell tumors, 57% of Sertoli-Leydig cell tumors, 33% of thecomas, and 14% of fibromas were calretinin positive. Inhibin was expressed in 60% of granulosa cell tumors, 71% of Sertoli-Leydig cell tumors, 43% of fibromas, and 33% of thecomas. Of 35 surface epithelial tumors (SET), 8% of serous papillary tumors were calretinin positive, whereas 8% of serous papillary tumors and 13% of poorly differentiated carcinomas expressed inhibin. WT1 was expressed in 29% of all endometrioid carcinomas, 10% of borderline mucinous tumors, and no mucinous carcinomas; however, most of the other SETs were positive (77% serous papillary and 88% poorly differentiated carcinomas). Among the SCST, WT1 stained only granulosa cell tumors (75%), though often weakly or variably. Calretinin has only slightly greater sensitivity (76% versus 65%) and equal specificity to inhibin (92%) in the differential staining of granulosa or Sertoli-Leydig cell tumors, that is, nonstromal SCST. Hence, calretinin cannot replace but could complement inhibin as part of an immunohistochemical panel used for diagnostically challenging SCST. Although WT1 should be reliably positive in non-mucinous SET, staining of granulosa cell tumors and lack of expression in a sizable subset of endometrioid carcinomas may confound interpretation.

Sertoli Cell Tumors of the Ovary

Ovarian Sertoli cell tumors are rare, and their morphologic spectrum, behavior, and factors influencing the latter are not clearly established. They may be mimicked by many different tumors, some of them more frequent than Sertoli cell tumors; immunohistochemistry may aid in this differential, but its role has not been analyzed in a large series. We studied the clinicopathologic features of 54 Sertoli cell tumors, including the immunohistochemical profile of 23 of them. The patients, 6 of whom had Peutz-Jeghers syndrome, ranged from 2 to 76 years of age (mean, 30 years). Eleven patients had estrogenic and 4 had androgenic manifestations. The tumors ranged from 0.8 to 30 cm, with the majority being in the range of 4 to 12 cm. They were all unilateral, usually solid, and often yellow. The predominant microscopic pattern was tubular, seen, albeit often only focally, in all tumors; other patterns were cords or trabeculae (28), diffuse (21), pseudopapillary (4), retiform (3), islands or alveolar arrangements (3), and spindled (3). The tubules were solid or hollow with the former being somewhat more common. Delicate septa were occasionally seen and were conspicuous in areas of one tumor. The stroma was abundant in 15 tumors with marked sclerosis in 4. The cells usually had pale to occasionally densely eosinophilic cytoplasm, but 6 tumors were composed of cells with prominent foamy cytoplasm, falling in the category of "lipid-rich" Sertoli cell tumor, and one had cells with clear non-foamy cytoplasm. Forty-four tumors were stage I (42 of them were stage Ia and 2 were stage Ic), 1 was stage II, 3 were stage III, and 6 were not adequately staged. Follow-up was available for 27 patients with stage I tumors, and all were alive and well at last follow-up except for 2 patients with stage Ia and 1 with stage Ic disease. Those 3 patients had pelvic-abdominal recurrences 18, 36, and 9 months, respectively, after the initial diagnosis. Two of the three clinically malignant stage I tumors had moderate to severe cytologic atypia and brisk mitotic activity (>5 or more mitoses/10 high power fields [HPFs]), and one of these had tumor cell necrosis. Among the 10 clinically benign stage I tumors with more than 5 years of follow-up, only 3 had >5 mitoses/10 HPFs, but none had more than mild cytologic atypia and none had tumor cell necrosis. Two of the three patients with stage III disease had follow-up information and one was alive at 16 months and the second developed splenic metastases 2 years after the initial diagnosis. Two of the three stage III tumors had at least moderate cytologic atypia and brisk mitotic activity. Immunohistochemical stains showed positivity for AE1/3-Cam5.2 in 15 of 23 tumors; Epithelial membrane antigen (EMA) was negative in all the tumors. Inhibin was positive in 18 of 22 tumors, calretinin in 10 of 20, CD99 in 19 of 22, vimentin in 17 of 18, smooth muscle actin in 4 of 18, neuron specific enolase in 8 of 16, S-100 in 2 of 20, and chromogranin was negative in all 21 cases studied. Although Sertoli cell tumors usually have a distinctive tubular pattern that facilitates the diagnosis, other patterns may occasionally predominate, causing confusion with various other primary and metastatic ovarian tumors. EMA, inhibin, and chromogranin represent the most helpful triad of immunomarkers serving to exclude two common mimics of Sertoli cell tumors (endometrioid carcinoma [inhibin-; EMA+; chromogranin-] and carcinoid tumor [inhibin-; EMA+; chromogranin+]). Although CD99 and calretinin are often expressed in these tumors, they are much less specific and not as helpful in the differential diagnosis. Most Sertoli cell tumors are stage I, unilateral, cytologically bland, and clinically benign, but occasional examples are high stage, and about 11% of stage I tumors have worrisome histologic features that may portend an adverse outcome. The tumors typically occur in young females, sometimes children who typically present with sexual precocity, and occasional patients have Peutz-Jeghers syndrome.

Significance of inhibin in reproductive pathophysiology and current clinical applications

The human reproductive process is regulated by complex mechanisms that involve many organs, including the brain, gonads and endocrine system. It has been more than 70 years since the name 'inhibin' was used to describe a substance produced in the gonads that negatively regulates pituitary secretion. Inhibin B controls FSH secretion via a negative feedback mechanism. It is a glycoprotein hormone secreted by the Sertoli cells of the testis and granulosa and theca cells of the ovary. Serum inhibin B concentrations are positively related to testicular volume and sperm counts. Current understanding of inhibin physiology and pathology in the human suggests that inhibin B may be of importance as a marker of Sertoli cell function in men with infertility and as a prognostic indicator in women undergoing ovulation induction therapy. Inhibin concentrations are elevated in patients with granulosa cell tumours and in post-menopausal women with mucinous ovarian cancers. Immunoreactivity against the inhibin alpha-subunit was identified in all cases of adrenal cortical adenoma and carcinoma, and levels are suppressed in the malignant prostate disease. This article discusses the structure, regulation and clinical use of inhibin and other related substances.