Dissociation of clinical and laboratory diagnosis in hypothyroidism

To assess the significance of clinical versus biochemical diagnosis of hypothyroidism using a clinical scoring index and optimize the therapeutic dose of levothyroxine in Indian patients.

Three hundred and eighty eight cases of primary hypothyroidism (male:female ratio 1:5.8) were clinically classified as hypothyroid, euthyroid or inconclusive by Billewicz score. TSH estimation was repeated at 6-8 week intervals and appropriate adjustments in levothyroxine dosage made till the TSH was within the normal range.

Of 388 biochemically confirmed hypothyroid subjects less than one fourth (21.6%) could be classified as hypothyroid, almost one half were euthyroid (48.4%) and the remaining (29.9%) fell in the inconclusive category according to Billewiz score. Of 227 patients who returned for complete follow up there was a positive correlation of replacement dose with age and initial weight in females, but not in males. Baseline TSH values were not found to have a significant correlation with the initial dose. The mean replacement dose of levothyroxine (T4) in our subjects was 109.4 +/- 24.05 microg/d (range 1.25-3.84 microg/kg).

Clinical parameters alone fare poorly in establishing an unequivocal diagnosis of hypothyroidism. A biochemical confirmation is mandatory. The replacement done of T4 was found to be independent of the basal TSH level.