[Anemia in hypothyroidism].
BACKGROUND
Anemias are diagnosed in 20-60% patients with hypothyroidism. Real values of the degree of anemia are estimated by radioisotopic analysis due to the lower volume of plasma in hypothyroidism causing false high levels of hemoglobin in blood. Anemia is often the first sign of hypothyroidism. Diagnosis of hypothyroidism should be considered in every case of anemia with uncertain etiology because sometimes signs of overt hypothyroidism needn't necessarily be evident. Microcytic, macrocytic and normocytic are regularly described anemias.


METHODS
Microcytic anemia is usually ascribed to malabsorption of iron and loss of iron by menorrhagia. Macrocytic anemia is caused by malabsorption of vitamin B12, folic acid, pernicious anemia and inadequate nutrition. Pernicious anemia occurs 20 times more frequently in patients with hypothyroidism than generally. Macrocytosis is found in up to 55% patients with hypothyroidism and may result from the insufficiency of the thyroid hormones themselves without nutritive deficit. Normocytic anemia, so-called uncomplicated anemia, arises due to thyroid hormones deficit itself not followed by nutritive deficit. This type of anemia is considered to be an adaptation to a decreased basal metabolism. Thyroid hormones directly or indirectly, through erythropoietin, stimulate growth of erythroid colonies (BFU-E, CFU-E). Normocytic anemia is characterized by reticulopenia, hypoplasia of erythroid lineage, decreased level of erythropoietin, mainly regular erythrocyte survival. Acanthocytosis findings in cytologic blood smear suggest hypothyroidism in about 90% of cases.
Antonijević
N
N
Poliklinika Vizim, Beograd.
Nesović
M
M
Trbojević
B
B
Milosević
R
R
D000740:Anemia / Q000209:etiology*; D000748:Anemia, Macrocytic / Q000209:etiology; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000175:diagnosis