The pituitaries of female rats subjected to various alterations in thyroid function were examined for changes in hypophyseal growth hormone content and acidophil morphology.
Thyroidectomy caused a significant decrease in the amount of growth hormone as well as a decrease in the acidophil granulation and population, whereas subsequent treatment with thyroxine allowed the pituitary structure and growth hormone content to return to normal. The pituitaries of unoperated rats fed a diet containing thyroid powder contained less growth hormone than those from normal controls, and the population and granulation of the pituitary acidophils were decreased.
The pituitary growth hormone content of thyroidectomized rats fed a diet containing 2,4-dinitrophenol was increased above thyroidectomy levels, but neither the pituitary cytology nor the hormonal level was restored to normal. The same diet fed to unoperated rats did not significantly alter the pituitary growth hormone levels and structure.