A comparison of the effects of altered thyroid and parathyroid function on reproduction in the rat.

Mild maternal hypothyroidism produced by surgical thyroidectomy resulted in significantly reduced food intake along with retarded reproductive performance in rats. Hyperthyroidism increased food consumption above the control level along with an increase in fetal resorptions which was the only parameter of reproductive performance altered by the twenty-second day of gestation. In animals which underwent pregnancies, reproductive performance suffered a further decline in the second gestation due to increasing duration of the hypothyroidism. Food restriction alone failed to duplicate these adverse effects on fetal development. Serum gonadotropins (LH and FSH) were not significantly altered by mild maternal hypothyroidism of hypoparathyroidism. The hematocrit and total blood volume of hypothyroid but not hypoparathyroid rats was significantly reduced from normal. Maternal hypoparathyroidism alone did not affect fetal development grossly.