Adverse Effects of Thyroid Hormones

The adverse health effects of thyrotoxicosis have been carefully documented and most practitioners are familiar with the clinical consequences for the patient. Until recently, many patients experienced the adverse effects of excessive thyroxine dosages, which can now be avoided by the application of highly sensitive immunometric assays for monitoring serum thyrotrophin (thyroid-stimulating hormone; TSH) levels. However, sensitive monitoring of serum thyrotrophin levels has led to the frequent recognition of biochemical subclinical hyperthyroidism (isolated suppression of thyrotrophin). Because of the increased recognition of this condition, the adverse effects of thyroxine therapy can be divided into those associated with subclinical hyperthyroidism and those associated with the euthyroid state.