Tyrosine hydroxylase activity and catecholamine content in the adrenals of young hypo- and hyperthyroid rats.

The weight, the tyrosine hydroxylase (TH) activity and the catecholamine (noradrenaline and adrenaline) content of young rat adrenals have been measured from birth to 20 days after birth in relation to hypo- and hyperthyroidism. Hypothyroidism impairs the adrenal growth, while hyperthyroidism has no effect on the adrenal weight. Hypothyroidism is associated with an enhancement of TH activity and catecholamine content. In hyperthyroid rats, the increase in TH activity and catecholamine content is slower than in controls. In adult animals, TH activity and catecholamine content are less affected by thyroid function.