Approach to a low tsh level: Patience is a virtue

Confronted with a low serum level of thyrotropin (thyroid-stimulating hormone,tsh),physicians should not jump to the conclusion that it is due to a hyperthyroid state,as other conditions and some drugs can be associated with a tsh level that is slightly low (0.1-0.4 μiu/ ml) or frankly suppressed (< 0.1 μiu/ml). this review discusses how to approach a low tsh,stressing the frequent need to reassess thyroid function before making a diagnosis,the underlying processes and the drugs that can be responsible,and the degree of tsh suppression and its role in the evaluation.