From the Guidelines
Inhibin levels should be measured in young adult patients as part of the diagnostic work-up for non-epithelial ovarian cancer, particularly in cases where germ cell tumors (GCTs) are suspected, as they can provide valuable information for diagnosis and treatment. According to the ESMO clinical practice guidelines for diagnosis, treatment, and follow-up of non-epithelial ovarian cancer 1, inhibin B levels, along with other markers such as hCG, a-FP, and LDH, should be assessed in young adult patients. Some key points to consider when evaluating inhibin levels include:
- Inhibin B levels can help confirm the diagnosis of certain ovarian tumors, such as adult granulosa cell tumors (AGCTs), when used in conjunction with an immunopanel of inhibin alpha, calretinin, and FOXL2, plus mutational analysis for FOXL2 (402C-G) 1
- Inhibin levels can vary throughout the menstrual cycle in women, with inhibin B typically highest during the follicular phase and decreasing after ovulation, while inhibin A rises during the luteal phase
- Normal inhibin B levels in women typically range from 10-200 pg/mL, although these levels can decline with age and reduced fertility potential
- Inhibin B levels can also reflect Sertoli cell function and spermatogenesis in men, with low levels suggesting impaired sperm production, and normal levels ranging from 100-400 pg/mL. Testing for inhibin levels is typically performed via blood samples, and interpretation requires consideration of age, sex, and menstrual timing in women.
From the Research
Inhibin Levels Overview
- Inhibin is a polypeptide hormone produced by the granulosa cells of the ovary, and its levels can be measured in body fluids as dimers of various sizes, each comprising an alpha- and beta-subunit 2.
- The normal range of inhibin in post-menopausal women is < 5 pg ml-1, in pre-menopausal women 2-80 pg ml-1, with 2-10 pg ml-1 in the follicular phase and 40-80 pg ml-1 in the luteal phase 2.
Inhibin Levels in Polycystic Ovary Syndrome (PCOS)
- Women with PCOS have higher concentrations of inhibin B and LH compared to normal women, and inhibin A is also elevated in untreated women with PCOS 3.
- Inhibin B levels in PCOS are inversely correlated with body mass index (BMI) and fasting insulin, and directly correlated with LH and sex hormone-binding globulin (SHBG) 4.
- The administration of human chorionic gonadotropin (hCG) to PCOS subjects suppresses inhibin B secretion, while short-term insulin suppression increases inhibin B 4.
Inhibin Levels in Follicular Fluid
- Inhibin B is approximately 10-fold higher than activin A and more than 100-fold higher than inhibin A in follicular fluid from both control and PCOS ovaries 5.
- There is no difference in activin A concentrations between PCOS and control follicles, and inhibin A concentrations are lower in PCOS follicles than in normal cohort follicles 5.
- Inhibin B concentrations are not different between PCOS follicles and normal cohort follicles, suggesting that PCOS is not associated with increased inhibin B concentrations in follicular fluid 5.
Clinical Applications
- Inhibin levels can be used as a tumor marker to determine response to therapy and predict recurrence in granulosa cell tumors of the ovary 2.
- Inhibin A and inhibin B can be measured in relation to the dynamics of follicular development in women with PCOS, and may be useful in monitoring treatment response 3.