The influence of preoperative drug treatment on the extent of hyperplasia of the thymus in primary thyrotoxicosis.

Thymic biopsies taken from women at the beginning of the operation of subtotal thyroidectomy were studied by the point-counting histometric technique. In all patients with primary thyrotoxicosis, the thymus is hyperplastic. After pretreatment with antithyroid drugs, the pattern of thymic involution with age is similar to, but at higher levels, than that in control groups of patients with non-toxic goitre in whom there is no evidence of immunological abnormality. By contrast, after propranolol pretreatment very little age involution is seen. The differences in the appearance of the thymus in female primary thyrotoxixosis patients prepared for operation with different drug treatment regimes are probably related to the pharmacological actions of the drugs and may indicate an interaction between primary immunological and secondary endocrinological factors in the disease process.