Thyrotropic hormone effects

The adenohypophysis is the part of the gland in which the tropic hormones are secreted They include the adrenocorticotropic hormone lACTHl. die thyrotropic hormone (TSH). and. somatotropin, as well as three hormones with pronounced effects upon the gonads the hormone prolactin, the follicle-stimulating hormone tFSHl and the luteinizing or interstitial cell stimulating hormone tLH or ISCH)... 

BIO. Borell, U., On the transport route of the thyrotropic hormone, the occurrence of the latter in different parts on the brain and its effect on the thyrodea. Ada Med. Scand. Suppl. 161, 1-227 (1945). 

The interchange of hormones between one tissue and another is of necessity effected through the blood, and the plasma is the great hi way of travel for these materials from the tissue where they are produced to those other tissues where their action is primarily exerted. Often, the hormones are present in blood in extremely low concentration so that it may be difficult or impossible to demonstrate the existence of a particular hormone by the assay of whole plasma. In some cases, however, a hormone may become readily demonstrable when concentrated in a particular plasma fraction, after suitable fractionation procedures. Such a result has indeed been demonstrated, for instance, by Professor F. L. Hisaw for the thyrotropic hormone, in plasma fractions obtained by the techniques later discussed in Part VI. 

Relaxin causes an increase in the biosynthesis of thyrotropic hormone as PLUNKETT (14) could confirm by radiological methods. Mechanism of action of relaxin was up till now not very clear. There is a reciprocal action between the other hormones and relaxin as pretreatment of estrogen is necessary for achievement of maximum activity of relaxin. STEINETZ (7) has published a hypothesis for the mode of action of relaxin on pubic symphysis, which is not applicable for other endocrine organs and particularly for general effects of relaxin. 

Located in close proximity to the primary capillary plexus in the hypothalamus are specialized neurosecretory cells. In fact, the axons of these cells terminate on the capillaries. The neurosecretory cells synthesize two types of hormones releasing hormones and inhibiting hormones (see Table 10.2). Each of these hormones helps to regulate the release of a particular hormone from the adenohypophysis. For example, thyrotropin-releasing hormone produced by the neurosecretory cells of the hypothalamus stimulates secretion of thyrotropin from the thyrotrope cells of the adenohypophysis. The hypo-thalamic-releasing hormone is picked up by the primary capillary plexus travels through the hypothalamic-hypophyseal portal veins to the anterior pituitary leaves the blood by way of the secondary capillary plexus and exerts its effect on the appropriate cells of the adenohypophysis. The hypophyseal hormone, in this case, thyrotropin, is then picked up by the secondary capillary plexus, removed from the pituitary by the venous blood, and delivered to its target tissue. 

In addition to its effect on GH secretion, octreotide can decrease tumor size—although tumor growth generally resumes after octreotide treatment is stopped. Octreotide also has significant inhibitory effects on thyrotropin secretion, and it is the treatment of choice for patients who have thyrotrope adenomas that oversecrete thyroid-stimulating hormone (TSH) and who are not good candidates for surgery. 

In addition to the classical thyrotropin, the anterior hypophysis seems to secrete other hormones with thyrotropic properties. These hormones have biological and immunological properties different from those of thyrotropin, but little is known about their chemistry. One long-acting thyroid stimulus (LATS) has a prolonged effect, and another short-acting thyroid stimulus (SATS) has a quicker effect. 

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