Acute in Vitro Stimulatory Effect of Thyrotropin Releasing Hormone (TRH) on T4 Secretion in Rat and Human Thyroid
TRH distribution is ubiquitous. In addition to the hypothalamus, TRH has been found in different parts of the brain, the islets of Langerhans, the testis, the placenta, and amniotic fluid (1). Evidence of TRH immunoreactivity has also been found in the porcine and human thyroid gland (2). Rat thyroid concentrates the injected labeled TRH (3). These findings suggest that TRH may have a direct effect on the thyroid gland. Prolonged intermittent or continuous infusion of TRH in rhesus monkeys at first induced a rise in TSH and T4, but while TSH went down to its basal value by the third day, T4 increased up to the ninth day (4). Similar results were reported in fasting humans (5). The late TSH decrease could result from the negative feedback of T4, but the fact that T4 continued to rise while TSH decreased suggests a stimulatory effect of TRH on T4 secretion.
KeywordsThyrotropin Release Hormone Human Thyroid Kinetic Pattern Adenylate Cyclase System Human Thyroid Tissue
Unable to display preview. Download preview PDF.
- 2.Iversen R, Laurberg P, and Weeke J. Ann Endocrinol 44: 90A, 1983.Google Scholar