**Core Concept**
Inhibin is a protein hormone secreted by the Sertoli cells in the testes and the granulosa cells in the ovaries. It plays a crucial role in regulating the production of follicle-stimulating hormone (FSH) by inhibiting its secretion from the anterior pituitary gland. Inhibin is composed of two subunits: alpha and beta, which are linked by a disulfide bond.

**Why the Correct Answer is Right**
Inhibin inhibits the production of FSH by binding to its receptor on the surface of pituitary gonadotrophs, which in turn reduces the secretion of FSH. This regulatory mechanism is essential for maintaining the balance between FSH and luteinizing hormone (LH) production, ensuring proper follicular development and ovulation in females and spermatogenesis in males. The inhibin-FSH feedback loop is critical for controlling the reproductive cycle.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is a feature of inhibin, as it is indeed a protein hormone secreted by Sertoli cells in the testes and granulosa cells in the ovaries.

**Option B:** This option is incorrect because inhibin does not stimulate the production of FSH; rather, it inhibits its secretion.

**Option C:** This option is incorrect because inhibin is not a stimulatory hormone; it is an inhibitory hormone that regulates FSH production.

**Option D:** This option is incorrect because inhibin is not a stimulatory hormone; it is an inhibitory hormone that regulates FSH production.

**Clinical Pearl / High-Yield Fact**
Inhibin levels can be used as a marker for ovarian reserve in females, with low inhibin levels indicating decreased ovarian function. This is an important consideration for women undergoing fertility treatments.

**Correct Answer:** B.