**Core Concept**
Prolactin is a hormone produced by the pituitary gland that plays a crucial role in lactation and breast milk production. The hormone stimulates the growth and differentiation of mammary glands during pregnancy and induces milk production postpartum.

**Why the Correct Answer is Right**
Prolactin binds to its receptor on the surface of mammary gland cells, triggering a cascade of intracellular signaling events that ultimately lead to the production and secretion of milk. This process is essential for the nourishment of the newborn. Oxytocin, another hormone produced by the pituitary gland, is involved in the milk ejection reflex, but it is not responsible for milk production.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided. Please fill in the correct options.
**Option B:** Incorrect, as oxytocin is involved in milk ejection, not milk production.
**Option C:** Incorrect, as thyroid-stimulating hormone (TSH) regulates thyroid function and has no direct role in lactation.

**Clinical Pearl / High-Yield Fact**
Prolactin levels increase during pregnancy and peak in the first few days postpartum, facilitating milk production. However, high prolactin levels can also be associated with conditions such as hyperprolactinemia, which can lead to galactorrhea and infertility.

**Correct Answer:** .