**Question:** Example of neurohormone: September 2012

**Core Concept:** Neurohormones are secreted by specialized cells in the nervous system and act on target organs or tissues to modulate their function. They are also known as neurotransmitters or neuromodulators.

**Why the Correct Answer is Right:** The correct answer is **Option C: Thyrotropin-releasing hormone (TRH)** because it is a neurohormone released from the hypothalamus, specifically the paraventricular nucleus. TRH acts on the anterior pituitary gland, stimulating the production and release of thyroid-stimulating hormone (TSH) and growth hormone (GH), leading to the regulation of thyroid function and growth.

**Why Each Wrong Option is Incorrect:**

A. **Option A: Epinephrine:** Epinephrine is a hormone secreted by the adrenal medulla, not a neurohormone. It acts through the sympathetic nervous system and the adrenal medulla.

B. **Option B: Glucagon:** Glucagon is a hormone secreted by the alpha cells of the pancreas, not a neurohormone. Glucagon acts on the liver and promotes gluconeogenesis and glycogenolysis, increasing blood glucose levels.

D. **Option D: Oxytocin:** Oxytocin is a hormone secreted by the posterior pituitary, not a neurohormone. Oxytocin acts on the posterior pituitary gland, causing uterine contractions during childbirth and milk ejection in lactating mammals.

**Clinical Pearl:** Understanding neurohormones helps to differentiate them from classical hormones, which are released by endocrine glands and act on target organs via the bloodstream. Neurohormones act directly on target tissues or organs, thus modulating their function without involving the circulation.