THYROID DISORDERS: A COMPREHENSIVE REVIEW OF CAUSES, DIAGNOSIS AND THERAPEUTIC MANAGEMENT

Thyroid disorders are common endocrine conditions that can substantially affect metabolic, cardiovascular and systemic health. The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), which regulate basal metabolic activity, energy expenditure, growth, development and cellular metabolism. Their synthesis is controlled by the hypothalamic-pituitary-thyroid axis through thyrotropin-releasing hormone and thyroid-stimulating hormone. Thyroid dysfunction is broadly classified as hypothyroidism or hyperthyroidism. Autoimmune disease, iodine deficiency or excess, thyroid surgery, radioactive iodine treatment and selected medicines may contribute to thyroid dysfunction. Diagnosis relies mainly on clinical assessment and biochemical testing, particularly serum TSH and free T4, with imaging and pathology used when indicated. Levothyroxine is the standard replacement treatment for primary hypothyroidism, while hyperthyroidism may be treated with antithyroid drugs, radioactive iodine or surgery. Thyroid dysfunction may also influence lipid and glucose metabolism and cardiovascular risk. This review summarizes the causes, pathophysiology, clinical manifestations, diagnosis, pharmacological management and systemic effects of thyroid disorders.