[Clinical and subclinical hyperthyroidism: two faces of the coin?]

We have made a prospective study of 23 patients diagnosed of subclinical hypothyroidism and 45 of overt hypothyroidism, aged 68.3-70.3 years and with a mean illness of 4.5 and 6.5 years respectively. It has been proved a higher prevalence of females in both groups. The most frequent clinical symptoms, similar in both groups, were fatigue, constipation and dyspnea. The most repeated initial diagnosis at the entry were prymary hypothyroidism, heart failure, hypertensive urgencies and stroke. We have found differences of statistical significance between the Free Thyroxine (fT4), triiodothyronine (T3), total serum cholesterol (CT), triglycerides (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C) and thyrotropin (TSH) initial and ending serum levels in patients with overt hypothyroidism (p < 0.05). We only have found significant differences in TSH serum levels in patients with subclinical hypothyroidism. The antithyroglobulin and antimicrobial antibodies, have been both positive in two and one patient respectively. Both are more useful as a predictor than their diagnostic value. The levothyroxine (L-T4) daily dose needed to normalize the TSH serum concentration, was lesser in subclinical hypothyroidism (71.8 micrograms opposite 107 micrograms-p < 0.001). We didn't find significant differences between the different groups in the time necessary for normalizing TSH. It seems that the L-T4 therapy should be started in all patients with subclinical hypothyroidism and TSH > or = 10 microU/ml or with TSH > 5 and goiter or with thyroid antibodies. The aim to reach is to normalize the TSH serum levels. The mean daily necessary L-T4 dose is 50-100 micrograms.