A comparison of plasma TSH levels in patients with diffuse and nodular non-toxic goiter.

Plasma TSH levels were measured in 115 euthyroid patients with simple goiter, of whom 52 had diffuse and 63 nodular enlargement of the thyroid gland, and in 191 euthyroid patients without goiter. There was no significant difference between the plasma TSH levels in the patients with diffuse goiter and the non-goitrous controls, implying that the maintenance of diffuse hyperplasia is not dependent upon a raised level of plasma TSH. On the other hand, plasma TSH levels in the patients with nodular goiter were significantly lower than those recorded in either the patients with diffuse goiter (P less than 0.01) or in the patients without goiter (P less than 0.0001), supporting the view that thyroid function may be autonomous in nodular goiters.