The epidermal response to change in thyroid status.

Epidermal dimensions, replication, and anabolic activity have been studied before and after treatment in 10 patients with thyrotoxicosis and 7 patients with hypothyroidism. Following treatment of thyrotoxicosis there was a significant decrease in epidermal thickness, and also in cell replication as measured by an autoradiographic labeling index technique. The rates of anabolic activity in the epidermis, as estimated by measuring the rates of incorporation of tritiated precursor compounds, were significantly reduced after treatment in the thyrotoxic group. There were increases in these same measurements in the hypothyroid group following treatment although their magnitude was not as great as that seen after treatment of thyrotoxicosis. There was a significant positive correlation between serum triiodothyronine and epidermal thickness, labeling index and proline incorporation, but no correlation could be detected between serum thyroxine iodine and any of the epidermal measurements. These findings indicate that the eidermis changes in structure and activity in thyroid disease, and that the changes are rapidly reversible. Furthermore, the correlations we have found suggest that the receptors for thyroid hormone in human skin are specific for triiodothyronine.