INHIBITORY EFFECTS OF (+ -)-TETRAHYDROPALMATINE ON THYROTROPIN-STIMULATING HORMONE CONCENTRATION IN HYPERTHYROID RATS/

The effects of (+/-)-tetrahydropalmatine ((+/-)-THP) on the hypothalam us-pituitary-thyroid system in rats were investigated. Thyroid functio n experiments indicated that (+/-)-THP produces significant decreases in thyroid function in hyperthyroid rats after 14 days of treatment. T hese effects were the same as those of propylthiouracil. However, prop ylthiouracil also decreased thyroid function in normal rats. Measureme nts of thyrotropin-stimulating hormone (TSH) demonstrated that (+/-)-T HP decreased TSH in hyperthyroid rats after 14 days of treatment; howe ver, propylthiouracil increased TSH in hyperthyroid rats. (+/-)-THP ha d no influence on TSH, or thyroid and pituitary weight in normal and h yperthyroid rats. We conclude that (+/-)-THP has an antithyroid functi on and the mechanism of action may be related to the inhibition of TSH in the pituitary.