[Evaluation of thyroid function in non-thyroid diseases]

The, in non-thyroidal illnesses, frequently occurring changes in the serum concentrations of peripheral thyroid hormones, are shown in patients with acute myocardial infarction, compensated and decompensated cirrhosis of the liver, renal insufficiency and in rheumatoid arthritis. The observed changes, (pathological) low total triiodothyronine, low or normal total thyroxine, and normal thyrotrophine), can make the diagnosis of hyperthyroidism impossible. Only in control measurements, after cessation of the simultaneous non-thyroidal illness, the peripheral thyroid hormone concentrations are found to be in the hyperthyroid range. The only way to establish the diagnosis, (or confirm the clinical suspicion), is to prove non-responsiveness of the pituitary to a TRH-stimulus. TRH-tests have, however, no diagnostic value in illnesses that affect pituitary function directly, such as terminal renal insufficiency. The diagnosis of hypothyroidism can be established by measurement of the basal thyrotrophine serum concentration (elevated) or by measurement of the serum concentrations of 3,3'5'-triiodothyronine (reverse T3), which is, according to a recent report, observed to be significantly decreased.