Thyrotropin--an episodically secreted hormone.

A recently developed highly sensitive immunoradiometric thyrotropin (TSH) assay capable to distinguish between euthyroid and hyperthyroid TSH-levels was used to evaluate the secretion-pattern of TSH in 10 healthy male subjects by taking blood via an indwelling venous catheter at 10 min intervals over 24 h. Visual analysis revealed a pulsatile pattern of hormone release with an average of 10.3 peaks/24 h. Evaluation by computer assisted programs such as the Santen-program (8.9 peaks/24 h, amplitude 0.60 mU TSH/l), the 'Pulsar'-program (6 peaks/24 h, amplitude 0.61 mU TSH/l) or power-spectrum analysis (11.9 peaks/24 h) showed similar results. These data suggest a pulsatile mechanism of TSH secretion similar to other pituitary hormones.