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Organ System Manifestations of Hypothyroidism: Haematological Changes

المؤلف:  Wass, J. A. H., Arlt, W., & Semple, R. K. (Eds.).

المصدر:  Oxford Textbook of Endocrinology and Diabetes

الجزء والصفحة:  3rd edition , p535

2026-04-27

276

Erythrocytes Anaemia is present in up to two- thirds of hypothyroid children and adolescents, and in about one- third of adults with hypothyroidism. Anaemia is usually mild. Anaemia in hypothyroidism may be a normochromic and normocytic anaemia due to the diminished oxygen requirements and decreased production of erythropoietin or may result from a specific depression of marrow that lacks thyroid hormone. The bone marrow generally shows mild hypoplasia with an increase in fatty marrow. The anaemia may be macrocytic, sometimes from deficiency of vitamin B12. Folate deficiency from malabsorption or dietary inadequacy may also cause macrocytic anaemia. The frequent menorrhagia and the defective absorption of iron resulting from achlorhydria may contribute to a microcytic hypochromic anaemia.

Leucocytes and Thrombocytes

 Granulocyte, lymphocyte, and platelet counts are usually normal in hypothyroidism. Leucopenia might indicate associated vitamin B12 or folic acid deficiency. Mean platelet volume can be decreased. The erythrocyte sedimentation rate (ESR) may be elevated in uncomplicated hypothyroidism.

Haemostasis

Hypothyroid patients may have bleeding symptoms such as easy bruising, menorrhagia, or prolonged bleeding after tooth ex traction. The most frequent defects in haemostasis are prolonged bleeding time, decreased platelet adhesiveness, and low plasma concentrations of factor VIII and von Willebrand’s factor (acquired von Willebrand syndrome type 1). This coagulopathy should be taken into account when planning invasive procedures in hypothyroid patients. The mild or moderate acquired von Willebrand syn drome is reversible after restoration of euthyroidism. There are also data suggesting existence of a hypercoagulation and hypofibrinolytic state, particularly in subclinical hypothyroidism.