## **Core Concept**
Inhibin is a protein complex that plays a crucial role in the regulation of the reproductive cycle by inhibiting the production of follicle-stimulating hormone (FSH) from the anterior pituitary gland. It is produced by the granulosa cells in the ovaries of females and by the Sertoli cells in the testes of males. The balance between activins and inhibins is vital for the proper functioning of the reproductive system.

## **Why the Correct Answer is Right**
Inhibin specifically inhibits the secretion of FSH from the anterior pituitary gland. This action is critical in the feedback mechanism that regulates the menstrual cycle and spermatogenesis. By reducing FSH levels, inhibin effectively decreases the stimulation of follicular growth in the ovaries and spermatogenesis in the testes. This process involves the **TGF-β (transforming growth factor-beta) signaling pathway**, where inhibin acts as a negative regulator.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because inhibin does not primarily inhibit luteinizing hormone (LH) release; that role is more closely associated with sex steroids like estrogen and testosterone.
- **Option B:** This option is incorrect because inhibin does not stimulate the release of FSH; instead, it does the opposite.
- **Option C:** This option might seem plausible since activin, a related protein, stimulates FSH release. However, the question specifically asks about inhibin.
- **Option D:** While inhibin does have effects on the reproductive system, stating it inhibits the release of **both LH and FSH** is not accurate; its primary and well-defined role is in inhibiting FSH.

## **Clinical Pearl / High-Yield Fact**
A key clinical correlation is that **inhibin levels can be used as a tumor marker** for certain types of ovarian and testicular tumors, such as granulosa cell tumors. Elevated levels of inhibin can indicate the presence of these tumors.

## **Correct Answer:** . FSH release