Somatostatin is secreted by –
**Core Concept**
Somatostatin is a hormone involved in regulating various endocrine functions, including the inhibition of growth hormone secretion and the modulation of gut motility and secretion. It plays a crucial role in maintaining homeostasis in the body.
**Why the Correct Answer is Right**
Somatostatin is primarily secreted by the delta cells of the pancreatic islets and the D cells of the gastrointestinal tract, including the stomach, small intestine, and colon. These cells release somatostatin in response to various stimuli, including gastrin, cholecystokinin, and secretin. Somatostatin then acts on nearby cells to inhibit the release of hormones such as insulin, glucagon, and gastrin, thereby regulating nutrient absorption and digestion.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because somatostatin is not secreted by the alpha cells of the pancreatic islets, which primarily release glucagon.
* **Option B:** This option is incorrect because somatostatin is not secreted by the beta cells of the pancreatic islets, which primarily release insulin.
* **Option C:** This option is incorrect because somatostatin is not secreted by the parathyroid glands, which primarily release parathyroid hormone.
**Clinical Pearl / High-Yield Fact**
Somatostatin analogs, such as octreotide, are used in the treatment of conditions like acromegaly, carcinoid syndrome, and pancreatic neuroendocrine tumors, which are characterized by excessive hormone production.
**Correct Answer: D. The D cells of the gastrointestinal tract, including the stomach, small intestine, and colon.**