Hematological Abnormalities in Thyroid Hormone Deficiency

Abstract

Thyroid hormones play a fundamental role in regulating hematopoiesis through their effects on bone marrow activity, erythropoietin production, and cellular metabolism. Hypothyroidism is associated with a wide spectrum of hematological abnormalities affecting red blood cells, white blood cells, and platelets. Anemia is the most common manifestation, particularly in hypothyroid patients, with reported prevalence ranging from approximately 26% to 31%, most commonly presenting as normocytic normochromic anemia. Leukopenia, especially neutropenia and lymphopenia, may also occur, while platelet abnormalities are less frequent and usually mild. These hematological changes are primarily attributed to impaired bone marrow function, reduced erythropoietin levels, and associated nutritional deficiencies such as iron, vitamin B12, and folate. Importantly, many of these abnormalities are reversible following correction of thyroid dysfunction. Early recognition of these alterations is essential, as they may precede overt thyroid disease and contribute to increased morbidity if left untreated.