Effects of blinding, pinealectomy and superior cervical ganglionectomy on free thyroxine index of male golden hamsters.

Blinding young male golden hamsters led to a depression of the plasma free thyroxine index after an 8 week period. Removal of either the pineal gland or the superior cervical ganglia of blind hamsters reversed the effects of blinding on free thyroxine index. No significant effects were observed 2 weeks after treatment. Previously reported effects of blinking, and removal of the pineal gland or the superior cervical ganglia on testicular weight were confirmed. A similar mechanism of pineal inhibition of thyroid function and gonadal function is suggested.