What is the Origin of Somatostatin Negative Feedback?

This principle is rooted in the classical understanding of the endocrine system's homeostatic control, specifically the counter-regulatory role of hypothalamic hormones on pituitary function. Somatostatin, also known as Growth Hormone-Inhibiting Hormone (GHIH), was named for its ability to inhibit somatotropin (GH) release, establishing its fundamental role in negative feedback. This mechanism is crucial for the pulsatile release pattern of growth hormone.

What is the Mechanism of Somatostatin Negative Feedback?

Somatostatin is released from neurosecretory nerve endings in the hypothalamus into the portal blood system, traveling to the anterior pituitary gland. Here, it binds to somatostatin receptors on somatotroph and thyrotroph cells, inhibiting adenylyl cyclase activity via G-inhibitory proteins. This cascade decreases intracellular cyclic AMP, thereby reducing the secretion of GH and TSH. Additionally, high levels of downstream hormones like Insulin-like Growth Factor I (IGF-I) stimulate somatostatin release, completing the long-loop negative feedback arc.

Somatostatin Negative Feedback ∞ Area

Somatostatin Negative Feedback

Meaning

Somatostatin Negative Feedback is a key regulatory mechanism within the hypothalamic-pituitary axis where the inhibitory hormone somatostatin acts to suppress the release of other endocrine factors. This feedback loop ensures that circulating levels of hormones like Growth Hormone (GH) and Thyroid-Stimulating Hormone (TSH) are tightly controlled and maintained within a narrow physiological range. It represents a vital dampening signal in the endocrine cascade.