The pituitary-thyroid axis effects on ocular and orbital tissues: a histological, histochemical, and morphometric study.

This work tests the notion that the effect of thyroid hormone on orbital and ocular tissues is mediated through its action on their lysosomal enzymes. Hyperthyroidism was produced in guinea pigs by thyroxin and TSH; hypothyroidism was induced by thiouracil. After treatment for 10 to 21 days, several ocular and orbital tissues were taken for histological, morphometrical, and histochemical examinations. High acid phosphatase activity was demonstrated in extraocular muscles, optic nerve and the retinal pigment epithelium of thyroxine- and TSH-treated animals. The findings fit the notion that the effects of thyroid hormones are mediated through lysosomes also in ocular and orbital tissues.