BENEATH THE SURFACE: UNDERSTANDING SUBCLINICAL HYPERTHYROIDISM

Abstract

Subclinical hyperthyroidism (SH) is a condition characterized by low thyroid-stimulating hormone (TSH) levels and normal levels of free thyroxine (T4) and triiodothyronine (T3). Its prevalence increases with age and is more common in iodine-deficient populations. The causes of subclinical hyperthyroidism can be divided into exogenous and endogenous factors. Exogenous subclinical hyperthyroidism results from the use of suppressive doses of thyroid hormones for various medical conditions, while endogenous subclinical hyperthyroidism may arise from underlying thyroid disorders like Grave's Disease, toxic multi-nodular goiter, and thyroiditis. Other factors, such as central hypothyroidism, pregnancy, non-thyroidal illnesses, and specific medications, can also lead to low TSH levels with normal T4 and T3. The prevalence of exogenous subclinical hyperthyroidism may vary depending on the chosen TSH cutoff levels. The prevalence is influenced by factors such as dietary iodine intake, with higher prevalence observed in populations with iodine deficiency. This review provides insights into the various causes and prevalence rates of exogenous subclinical hyperthyroidism, offering a comprehensive understanding of this condition.