From the Guidelines
No, somatostatin is not a tropic hormone. Somatostatin is actually an inhibitory hormone produced primarily in the hypothalamus, pancreas, and gastrointestinal tract. Unlike tropic hormones, which stimulate other endocrine glands to produce and secrete their own hormones, somatostatin functions by inhibiting the release of numerous hormones. It suppresses the secretion of growth hormone and thyroid-stimulating hormone from the pituitary gland, as well as insulin and glucagon from the pancreas. In the digestive system, it inhibits the release of gastrointestinal hormones and reduces intestinal motility and blood flow. Somatostatin's inhibitory role contrasts with true tropic hormones like ACTH, TSH, and gonadotropins, which stimulate target glands to produce hormones. This distinction is important for understanding endocrine regulation, as somatostatin serves as a regulatory brake within multiple physiological systems rather than a stimulatory signal.
Key Points
- Somatostatin is an inhibitory hormone, not a tropic hormone
- It inhibits the release of various hormones, including growth hormone, thyroid-stimulating hormone, insulin, and glucagon
- Somatostatin analogues, such as octreotide and lanreotide, are used to manage symptoms of neuroendocrine tumors and other conditions, as seen in studies 1
- These analogues have been shown to improve symptoms and quality of life in patients with carcinoid syndrome and other conditions, as demonstrated in studies 1
Clinical Implications
- Somatostatin's inhibitory role is crucial in understanding its effects on various physiological systems
- Somatostatin analogues can be used to manage symptoms and improve quality of life in patients with certain conditions, as supported by studies 1
- The distinction between somatostatin and tropic hormones is important for understanding endocrine regulation and making informed clinical decisions, as highlighted in studies 1
From the FDA Drug Label
Octreotide exerts pharmacologic actions similar to the natural hormone, somatostatin. The FDA drug label does not answer the question.
From the Research
Definition of Tropic Hormone
A tropic hormone is a hormone that regulates the function of another endocrine gland.
Somatostatin's Role
Somatostatin is known to inhibit the release of various polypeptide hormones, including insulin, glucagon, gastrin, thyroid-stimulating hormone, and growth hormone 2. It acts as a hypophyseotropic hormone, regulating the release of hormones from the pituitary gland 3.
Mechanism of Action
Somatostatin's mechanism of action involves binding to specific receptor subtypes, of which there are at least five (SSTR1-5) 4. These receptors are found in various tissues, including the pituitary gland, pancreas, and gut. Somatostatin's inhibitory effects on hormone release are mediated through these receptors, with different subtypes playing distinct roles in regulating different hormones 5.
Evidence for Tropic Hormone Classification
Given its role in regulating the release of hormones from other endocrine glands, somatostatin can be considered a tropic hormone. Its ability to act on the pituitary gland to inhibit the release of growth hormone, for example, is a key characteristic of a tropic hormone 3, 4. Additionally, its effects on the pancreas, where it inhibits the release of insulin and glucagon, further support its classification as a tropic hormone 2, 5.
Key Points
- Somatostatin inhibits the release of various polypeptide hormones
- It acts as a hypophyseotropic hormone, regulating the release of hormones from the pituitary gland
- Somatostatin binds to specific receptor subtypes (SSTR1-5) to exert its effects
- Its inhibitory effects on hormone release are mediated through these receptors
- Somatostatin can be considered a tropic hormone due to its role in regulating the release of hormones from other endocrine glands