THE USE OF THYROTROPIC HORMONE (TSH) IN THE DIAGNOSIS OF MYXEDEMA*†

Abstract

UNTIL recently, the diagnosis of pituitary myxedema has depended upon the association of hypothyroidism with adrenocortical in sufficiency and very low or absent urinary follicle-stimulating hormone (FSH) levels (1). However, the observation that proven primary thyroid myxedema may be accompanied by evidence of adrenocortical insufficiency (2, 3, 4, 5) and low or absent urinary FSH (3) has shed doubt upon the validity of this concept. In certain instances, the differential diagnosis between primary thyroid and pituitary myxedema may be extremely difficult. With the availability of relatively pure thyroid-stimulating hormone (TSH), a technique may now be employed which specifically tests the ability of thyroid tissue to respond to pituitary stimulation. This test is based upon two premises: first, that primary myxedema is due to failure of the thyroid gland, the tissue of which cannot be stimulated to function normally; second, that pituitary myxedema is due to a failure of the pituitary gland to stimulate the thyroid gland, which is, however, potentially capable of being stimulated.