Assess the function of the antral follicles the dominant follicle/corpus luteum of the ovaries in women
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R).
It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Male: < 3.6 pg/mL
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. In recent years, the inhibin proteins have been characterized and specific immunoassays have been developed for both inhibin A and inhibin B. These hormones are members of the transforming growth factor-B superfamily. 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. Normal men do not produce measurable levels of inhibin A. In young girls, the concentrations of inhibin A increase as puberty progresses. Therefore, the measurement of inhibin A could aid in determining gonadal maturity and diagnosing precious 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 themenopausal transition, the circulating follicular phase levels of inhibin decline. 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's syndrome and in predicting pre-eclampsia. This ultrasensitive inhibin A test was not designed for these applications and instead can be used to accurately measure the lower inhibin A levels that are found in non-pregnant individuals.