How to detect hypothyroidism when screening tests are normal. Use of the TRH stimulation test.

In this study, 65 women and two men were examined because of symptoms suggesting hypothyroidism (eg, tiredness, lack of energy, weight gain, dry skin, cold intolerance, constipation, galactorrhea, menstrual disturbances). Some also demonstrated biochemical abnormalities (eg, hyperlipoproteinemia, elevation of creatine phosphokinase). Serum thyroxine (T4) and triiodothyronine (T3) and T3 uptake were normal in all patients. The thyrotropin-releasing hormone (TRH) test differentiated the patients into two groups: Group 1 (47 patients) had an exaggerated response of thyroid-stimulating hormone (TSH) to TRH; group 2 (20 patients) had a normal TSH response. Compared with group 2, the group 1 patients had a higher incidence of typical hypothyroid symptoms and goiter and responded more readily to levothyroxine therapy. We concluded that these patients had borderline hypothyroidism. Results of basal thyroid function tests may be within normal limits in such a condition. The TRH test, then, appears to increase diagnostic accuracy and should be routinely performed in patients who have symptoms suggesting hypothyroidism but normal results of basal thyroid function tests.