Abstract
Summary
The effect of various levels of estradiol benzoate (E.B.) upon thyroxine secretion rate (TSR) has been studied in young mature female rats. A dose of 3.6 μg/day E.B. caused significant increase of 35.5% in TSR over average control value of 1.24 μg/100 g/day l-thyroxine while 1, 15 or 50 μg/day had no effect. In another experiment, body weight and thyroid weight/100 g were not affected by injecting 1 or 3.6 μg/day E.B. for 5 days. Thyroid weight/100 g was significantly increased while appetite and body weight were markedly reduced following 15 or 50 μg/day for same period. Pituitary weight/100 g was significantly increased in all but the 1 μg/day group. Adrenal weights/100 g were lower in all groups with significant depression occurring in 50 μg/day group. These data are discussed in relation to stimulation or depression of thyroid activity by estrogen.
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