Abstract
Summary
Thyroid hormone secretion rate (TSR) of 62 female rats at 30 days of age was estimated as 1.24 μg L-T4/100 g body wt. During the next 8 weeks the rats were maintained in continuous light or continuous darkness or a normal light-dark schedule. After 8 weeks of continuous light treatment, the TSR of this group was increased 21% (p.05) above the control group. The TSR of the control group and those in total darkness were not significantly different.
Constant light significantly increased ovarian, uterine, and pituitary weight. A significant decrease of 25% was observed in pineal weight. The weight of adrenals, thymus, and thyroid glands were unaffected. The weights of endocrine glands of the rats in continuous darkness were not significantly different from those of the control group.
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