Inhibin

HI just a quick question my gyno/oncologist who i have just been referred to by my GP has ordered the Inhibin test the lady told me it is rare to do taht test is it rare and what does it tell. I have been referred to her due to a worried gp. Thank you

[Annekathryn Goodman, M.D.]

Hi There

Historically, inhibin was the name given to a component of serum that was found to inhibit secretion of follicle stimulating hormone (FSH) by the pituitary.1,2 In recent years, the inhibin proteins have been characterized and specific immunoassays have been developed for both inhibin A and inhibin B.1 These hormones are members of the transforming growth factor-B superfamily.1,2 Structurally, they consist of dimers of two dissimilar protein subunits. The alpha-subunit is common to both inhibins. The alpha-subunit of inhibin B is covalently linked to a beta-B subunit by disulfide bridges. In women, inhibin A is made largely by the dominant follicle/corpus luteum.1 Normal men do not produce measurable levels of inhibin A.1
In young girls, the concentrations of inhibin A increase as puberty progresses.3,4 Therefore, the measurement of inhibin A could aid in determining gonadal maturity and diagnosing precocious puberty in girls. Once women reach reproductive age, inhibin A levels change with the menstrual cycle. Levels rise through the follicular phase to a maximum in the luteal phase with an intermediate peak at ovulation. In the early perimenopausal phase of the menopausal transition, the circulating follicular phase levels of inhibin decline.5 In postmenopausal women, inhibin A levels fall to <5 pg/mL.

During pregnancy, the fetoplacental unit produces relatively large amounts of inhibin A. Assessment of inhibin A concentration relative to gestational age of fetus has been applied extensively to prenatal screening for Down syndrome and in predicting pre-eclampsia.1


Inhibin B is a protein hormone produced by your ovaries. It works to inhibit FSH, which is responsible for helping your follicles to develop. Levels of Inhibin B decrease with age.

Inhibin B is actually secreted directly by small, developing follicles in your ovaries. During the follicular phase of ovulation, small follicles eventually develop into mature eggs, ready for fertilization. Inhibin B has a sister hormone called Inhibin A, which is also produced by the ovaries.

The Day 3 Inhibin B Test is used in order predict ovarian reserve, including egg quality and eqq quantity. Because Inhibin B is produced directly by ovarian follicles, the amount of Inhibin B in your blood directly correlates to the number of eggs that you have in your ovaries. Inhibin B can also predict the ability of your ovaries to produce more follicles

A test for serum inhibin has been developed which is able to diagnose granulosa cell tumors and mucinous carcinomas with high accuracy. Granulosa cell tumors are malignancies of the cells that surround the egg and produce hormones.

Inhibin is being looked at as a screening test for the more common epithelial ovarian cancer but I do not believe the word is in yet as to whether it is a good screening test
take care