Serum Thyrotrophin in Myxedema and in Asymptomatic Atrophic Thyroiditis

Abstract

With the use of the McKenzie bio-assay, the serum TSH (thyrotrophin) level has been measured in 15 patients with full-blown myxedema, in 45 subjects without clinical signs of thyroid disease but with serological and biological signs of atrophic thyroiditis, and in 45 normal subjects matched for age and sex. The lack of sensitivity of the method used prevented the detection of serum TSH levels below 17 mU/100 ml. In the normal subjects used as controls the measurable values ranged from 17 to 33 mU/100 ml, but undetectable levels were frequently observed and their incidence increased with age. In the patients with “asymptomatic atrophic thyroiditis” the TSH levels were statistically higher than in the controls. In the cases of primary spontaneous myxedema as well as in cases of cretinism, post-therapeutic hypothyroidism and Hashimoto's thyroiditis with hypothyroidism, TSH was consistently detectable at normal or elevated levels. The data suggest that in asymptomatic atrophic thyroiditis a condition of clinical euthyroidism is only maintained by the increased pituitary thyrotrophin secretion.