TSH and Thyroidal Responses to Continuous and Intermittent TRH Administration
Several hypothalamic-releasing hormones have been isolated, and the responses to them characterized. Single doses cause transient dose-dependent increases in the serum levels of the respective pituitary hormones. The responses to prolonged administration vary, depending on the method and frequency of administration, and are determined by factors such as inhibition by target gland hormones, depletion of hormone stores, and down-regulation of pituitary receptors. With regard to TRH, short-term infusions raise serum TSH for the duration of the infusion, and prolonged intrathecal TRH administration causes sustained increases in serum TSH, T4, and T3 (1–5). However, repeated individual intravenous or oral doses of TRH result in reduced TSH responses after several days (6–9). This study was undertaken to compare the TSH and thyroidal responses to the same total TRH dose given intermittently and continuously in the same subjects.
KeywordsNorth Carolina School Pituitary Receptor Thyroidal Response Hormone Store Repetitive Bolus
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