Observations of the anterior pituitary cytology in the phenobarbital treated rat

Abstract

The effect of sodium phenobarbital on the thyroid and pituitary have been studied in the male albino rats. It was found that prolonged administration of phenobarbital exerted a marked goitrogenic influence on the thyroid. The weight of phenobarbital treated gland was about 4 times greater than that in the control animals. The goitrogenic growth of thyroid was accompanied by a pronounced hypertrophy and hyperplasia of the thyroid follicular cells and complete disappearance of intrafollicular colloid. The observations on the pituitary cytology also show that phenobarbital administration brings about easily demonstrable changes in the microscopic appearance of the anterior pituitary gland. The changes involved both hypertrophy and degranulation of the thyrotrophic cells and appearance of the large vacuolated cells of thyroidectomy. The observed cytological modification of the anterior pituitary gland shows that chronic administration of phenobarbital leads to increased secretion of thyrotropic hormone. It was suggested that the pituitary thyrotropic hypersecretion induced by phenobarbital results either from supression of thyroid hormone synthesis or from a changed peripherial metabolism of thyroid hormone. © 1971 Springer-Verlag.