THE EFFECT OF TRYPAN BLUE ON THYROID FUNCTION IN THE RAT11

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Abstract
Four ml. of a 0.5% saline solution of trypan blue were injected intraperitoneally once or twice daily for varying periods of time. Six days after the injections, thyroid weight and serum PBI had decreased to 60% and 25% of normal, respectively, while thyroidal radioiodine uptake was suppressed to 15% of the normal value. Thyroid hormone secretion was inhibited for about 14 hours by a single injection of trypan blue; continuous inhibition was produced by repeated injections. Exogenous TSH given to these treated rats caused thyroid hormone secretion to resume. Adrenal weight increased after trypan blue administration, but there was no change in testis weight. Pituitary weight was slightly less in treated animals. It is believed that trypan blue treatment specifically inhibits pituitary TSH secretion, causing secondary hypofunction of the thyroid.