Thyroid stimulating hormone release factor

Hypothyroidism (thyroid hormone deficiency) may result from autoimmune disease (Hashimoto s disease) or from deficient synthesis of TSH or TRH (thyroid-stimulating hormone-releasing factor). Because adequate ingestion of iodine is a prerequisite for thyroid hormone synthesis, iodine deficiency also causes hypothyroidism. In children, thyroid hormone deficiency (called cretinism) causes depressed growth and mental retardation. Severe hypothyroidism in adults (myxedema) results in symptoms such as edema (abnormal fluid accumulation) and goiter. Hypothyroidism is usually treated with hormone replacement therapy. 

Thyroid stimulating hormone releasing factor (TSH-RF), sometimes known as thyrotrophin-releasing factor (TRF). 

The class III cytokine receptor family includes two TNE receptors, the low affinity NGE receptor and 7-ceU surface recognition sites that appear to play a role in proliferation, apoptosis, and immunodeficiency. TNE-a (- 17, 000 protein) is produced by astrocytes and microglia and can induce fever, induce slow-wave sleep, reduce feeding, stimulate prostaglandin synthesis, stimulate corticotrophin-releasing factor and prolactin secretion, and reduce thyroid hormone secretion. TNE-a stimulates IL-1 release, is cytotoxic to oligodendrocytes, and reduces myelination this has been impHcated in multiple sclerosis and encephalomyelitis. Astrocyte TNE-a receptors mediate effects on IL-6 expression and augment astrocytic expression of MHC in response to other stimulants such as lEN-y. 

Otfier fiormones accelerate tfie release of free fatty acids from adipose tissue and raise tfie plasma free fatty acid concentration by increasing the rate of lipolysis of the triacylglycerol stores (Figure 25—8). These include epinephrine, norepinephrine, glucagon, adrenocorticotropic hormone (ACTH), a- and P-melanocyte-stimulat-ing hormones (MSH), thyroid-stimulating hormone (TSH), growth hormone (GH), and vasopressin. Many of these activate the hormone-sensitive hpase. For an optimal effect, most of these lipolytic processes require the presence of glucocorticoids and thyroid hormones. These hormones act in a facilitatory or permissive capacity with respect to other lipolytic endocrine factors. 

Thyroid-Releasing Hormone Toxic Substances Control Act Thyroid Stimulating Hormone Treatment Technique Threshold of Toxicological Concern Target-organ Toxicity dose Unscheduled DNA Synthesis Uncertainty Factor United Nations... 

The secretion of anterior pituitary hormones is controlled in part by hypothalamic regulatory factors that are stored in the hypothalamus and are released into the adenohypophyseal portal vasculature. Hypothalamic regulatory factors so far identified are peptides with the exception of dopamine. Secretion of anterior pituitary hormones is also controlled by factors produced more distally that circulate in the blood. Predominant control of hormone production may be relatively simple, as with thyroid-stimulating hormone (TSH), the production of which is primarily stimulated by thyrotropin-releasing hormone (TRH) and inhibited by thyroid hormones, or it may be complex, as with prolactin, the production of which is affected by many neurotransmitters and hormones. 

Thyroid Stimulating Hormone Thyrotropin-releasing hormone Thyroxin Binding Globulin Tissue Factor... 

Fig. 8. Relationship between 20-minute level of serum thyroid-stimulating hormone (TSH) after 200 ng of thyrotropin-releasing factor (TRH) i.v. and the 6-hour thyroidal uptake after one week on triiodothyronine (Ts). 100 /ig daily.

Thyrotropin releasing hormone, thyrotropic hormone releasing factor(TRF), thyroliberin Pyr-His-Pro-NH2 (Pyroglutamyi-L-hktidyl-L-prolinamide), M, 262. The identical hormone is found in all hitherto investigated species. Secretion of TRF is promoted by neurotransmitters, e.g. noradrenalin, and inhibited by serotonin. TRF stimulates the anterior pituitary to synthesize and secrete thyrotropin, which in turn stimulates the thyroid gland to secrete thyroxin and triiodothyronin. The latter two hormones exert a negative feedback on the secretion of TRF and thyrotropin. TRF also stimulates the secretion of prolactin and acts as a neurotransmitter in the central nervous system. 

Thyroid Stimulating Hormone (TSH) Releasing Factor. T - The chemistry and physiology of TRF has recently been reviewed -. The structure of ovine TRF was conclusively established by high resolution mass spectrometry and additional chemical characterization to be C lu-His-Pro-NH2. Subsequently, porcine TRF was shown conclusively to have the same structure . ... 

Thyrotropin-releasing factor (TRF) is produced in the hypothalamus and arrives at the pituitary via the hypophyseal portal blood system. TRF mediates the release of thyrotropin from the anterior hypophysis. The thyrotropin release is inhibited by thyroxine, presumably free thyroxine, and the inhibition is dose dependent. Thus excessive levels of thyroxine depress thyrotropin release, and lower thyroxine levels result in increased thyrotropin release from the anterior pituitary. TSH, in turn, stimulates thyroid hormone synthesis and secretion by the thyroid gland. Thyroxine and triiodothyronine are bound to specific binding proteins in the blood. The amounts and binding constants of the specific thyroid-binding proteins, together with the rate of thyroid hormone release from the thyroid, determine the amount of free thyroxine in the blood. Free thyroxine levels are determined not only by the rate of... 

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