Abstract
Systemic injection of marihuana distillate extract, of whichΔ9-tetrahydrocannbinol (Δ9-THC) is the major single constituent, inhibits the release of radioiodine from the thyroid gland of the rat. Administration of thyroid stimulating hormone (TSH) resulted in increased output of iodine in animals pretreated withΔ9-THC. These data suggest that reduced TSH secretion is the primary cause of the thyroid inhibition induced by THC. Bilateral electrolytic lesions in the region of the medial mammillary nuclei of the hypothalamus prevented the decrease in pituitary-thyroid activity induced by THC, whereas lesions in the rostral hypothalamus did not effect the response. These results indicate that THC inhibits pituitary-thyroid function due to an action on neurons in the caudal hypothalamus. The possibility is discussed that these effects are due to stimulation of specific inhibitory centers rather than depression of neurons responsible for tonic release of TSH. Marihuana appears to have a similar action to morphine in modifying pituitary-thyroid function.
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