Abstract
Mouriz et al. (1) have recently reported that KI injected after propylthiouracil (PTU) given in incompletely blocking doses increased the thyroidal synthesis of iodothyronines. They suggested that this led to enhanced secretion of thyroid hormones, and hence decreased production of TSH, which then was reflected by a decline of the previously elevated thyroidal 131I release rate. However, we have found that KI leads to a rapid reduction of thyroidal 131I release in hypophysectomized rats given TSH and 5 or 30 rag PTU daily. Depressing effects of KI on thyroidal 131I release therefore do not have to involve altered secretion of TSH. Unlike Mouriz et al. (1), we did not find that KI increased the percentage of 131I in the iodothyronine fraction of thyroid homogenates of intact rats given incompletely blocking doses of PTU, nor did it have such an effect in similarly treated hypophysectomized, TSH-injected rats. (Endocrinology 81: 643, 1967)
Published Version
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