Effect of Hyperthyroidism on Body Weight Gain and Feed Consumption in Male and Female Rats. ∗

Summary

Male and female rats of Sprague-Dawley-Rolfsmeyer strain, age 26 days, were injected daily with 3.0, 6.0, 9.0, and 12.0 μg L, thyroxine/100 g BW for 200 days in comparison with normal groups. Lowest level was 3 X mean TSR and equal to highest rate observed in lactating rats. In females, weight gain was reduced by less than 10% in comparison with controls with increasing age, and no trend toward greater weight restriction was observed on higher levels of T₄. In males, increased weight restriction appeared at 40 days and beyond, and was more marked than in females. Levels of 6 μg and above permitted gain equal to 60 to 70% of that of controls. Food consumption increased progressively on higher T₄ levels but females showed less increase than did males.