Inhibin is secreted by-
**Core Concept**
Inhibin is a **hormone** that plays a crucial role in the regulation of the **reproductive cycle**. It is involved in the negative feedback mechanism of **follicle-stimulating hormone (FSH)** secretion. Inhibin is produced by the **gonads**, specifically by the **Sertoli cells** in the testes and the **granulosa cells** in the ovaries.
**Why the Correct Answer is Right**
The correct answer is related to the source of inhibin secretion, which is the **gonads**. In the testes, inhibin is secreted by the **Sertoli cells**, while in the ovaries, it is secreted by the **granulosa cells**. This hormone inhibits the production of **FSH** by the **anterior pituitary gland**, thus regulating the reproductive cycle.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not the primary source of inhibin secretion.
**Option B:** Incorrect as it is not related to inhibin secretion.
**Option C:** Incorrect because it is not the correct source of inhibin secretion.
**Clinical Pearl / High-Yield Fact**
Inhibin plays a crucial role in the diagnosis of certain **reproductive disorders**, such as **ovarian cancer** and **testicular cancer**.
**Correct Answer:** D. Granulosa cells and Sertoli cells.