**Core Concept**
Inhibin is a protein complex that plays a crucial role in the regulation of the reproductive axis by inhibiting the production of follicle-stimulating hormone (FSH) by the pituitary gland. It is produced by the granulosa cells of the ovaries in females and by the Sertoli cells of the testes in males.

**Why the Correct Answer is Right**
Inhibin is secreted by the granulosa cells of the ovaries in response to follicle-stimulating hormone (FSH) stimulation. The inhibin complex consists of two subunits: alpha and beta. The beta subunit is specific to either the beta-A or beta-B subunit, which are encoded by different genes. The inhibin complex binds to the inhibin receptor on the surface of the pituitary gland, leading to a decrease in FSH production. This negative feedback mechanism helps to regulate the menstrual cycle and maintain reproductive homeostasis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, but it is likely incorrect because inhibin is not secreted by the ovarian stroma or theca cells.
**Option B:** This option is not specified, but it is likely incorrect because inhibin is not secreted by the adrenal glands or other endocrine tissues.
**Option C:** This option is not specified, but it is likely incorrect because inhibin is not secreted by the hypothalamus or other regions of the brain.

**Clinical Pearl / High-Yield Fact**
Inhibin is a key regulator of the reproductive axis, and its dysregulation can lead to disorders such as polycystic ovary syndrome (PCOS) and premature ovarian failure.

**Correct Answer:** D. Sertoli cells of the testes and granulosa cells of the ovaries.