Effects of Thyroid Hormone (T4, T3 ), Bromocriptine And Triac on Inappropriate TSH Hypersecretion

Inappropriate TSH hypersecretion was diagnosed in a 34 years old woman. Earlier she had been treated by ablative therapy for hyperthyroidism. The present diagnosis was based on elevated basal serum TSH levels despite elevated serum free thyroid hormone level. Her TSH responses to TRH (peak value 240 mu/I) was high. Her albumin and prealbumin levels were normal. The serum TBG level, alpha subunit of TSH and pituitary CT scans were nora_ml. Despite mild clinical hyperthyroidism, peripheral indices of thyroid hormone action were normal. In view of the possibility that prolonged pituitary thyrotrophic stimulation is deterimental, various therapeutic approach to suppress TSH levels, but are very poorly tolerated. Acute administration of L-dopa or bromocriptine reduced serum TSH levels, but this was not seen during long term therapy. Triac treatment lowered serum TSH levels, and the drug was well tolerated. Serum TSH responses to TRH were not blunted during T 3, T4 or triac treat­ments. Somatostatin also reduced serum. TSH levels, but did not potentiate the effect of low dose T 3 therapy. Our results suggest that the patients had unbalanced pituitary and peripheral thyroid hormone resistance, predominantly at the pituitary level. Of the drugs studied, triac seemed to be the most suitable one.