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TRH may cause nausea, vomiting and some patients experience an urge to urinate. [citation needed] Rarely, TRH may cause blood vessel constriction leading to hemorrhage in patients with pre-existing pituitary tumors. Accordingly, patients should be advised about the risks, albeit rare, of TRH testing. [2]
Thyrotropin-releasing hormone (TRH) is a hypophysiotropic hormone produced by neurons in the hypothalamus that stimulates the release of thyroid-stimulating hormone (TSH) and prolactin from the anterior pituitary. TRH has been used clinically for the treatment of spinocerebellar degeneration and disturbance of consciousness in humans. [1]
A common cause for hyperprolactinemia is prolactinomas and other tumors arising near the pituitary. These adjacent tumors, such as those that cause acromegaly, can physically compress the pituitary stalk and block the flow of dopamine from the hypothalamus to the pituitary gland, causing prolactin levels to increase.
The neurotransmitters implicated in the control of nausea and vomiting include acetylcholine, dopamine, histamine (H1 receptor), substance P (NK-1 receptor), and serotonin (5-HT3 receptor). There are also opioid receptors present, which may be involved in the mechanism by which opiates cause nausea and vomiting.
Graves' disease is the cause of about 50% to 80% of the cases of hyperthyroidism in the United States. [1] [7] Other causes include multinodular goiter, toxic adenoma, inflammation of the thyroid, eating too much iodine, and too much synthetic thyroid hormone. [1] [2] A less common cause is a pituitary adenoma. [1]
The TRH stimulates the anterior pituitary to produce thyroid-stimulating hormone (TSH). The TSH, in turn, stimulates the thyroid to produce thyroid hormone until levels in the blood return to normal. Thyroid hormone exerts negative feedback control over the hypothalamus as well as anterior pituitary, thus controlling the release of both TRH ...
TRH stimulates the thyrotropic cells through the use of a phospholipase C second messenger system. [1] TRH binds to a class A G protein-coupled receptor on the surface of a thyrotropic cell, which is known as the thyrotropin-releasing hormone receptor (TRHR). Strong hydrogen bonding interactions stabilize the binding of TRH to TRHR.
Some chemotherapeutic agents may not cause nausea and vomiting on their own, but may when used in combination with other agents. [6] Regimens that are linked to a high incidence (90% or higher) of nausea and vomiting are referred to as "highly emetogenic chemotherapy", and those causing a moderate incidence (30–90%) of nausea and vomiting are ...