Anemia in children and adolescents with hypothyroidism.

In a review of 17 adolescents and children (excluding newborns) with definite clinical signs, symptoms, and laboratory findings of hypothyroidism, 11 patients (65%) had anemia. The mean corpuscular volume (MCV) of the red blood cells was either macrocytic or normocytic. The hemoglobin did not correlate with the serum thyroxine level. Anemia occurred only in those patients with heights below the third percentile, but there was no similar correlation with weights. Of the 10 patients who had radiographs for bone age, all showed severe delay (47 to 103 months) and had heights below the third percentile. Nine of these patients were anemic, but the severity of the anemia did not correlate with the delay in bone age. Neither microcytic anemia nor pernicious anemia, noted in many adult hypothyroid patients, was found in the children and adolescents with hypothyroidism studied here. The "uncomplicated" anemia secondary to hypothyroidism responded to thyroid replacement therapy alone. Anemia can be the most prominent feature of hypothyroidism. In patients with mild to moderate anemia of unknown origin, especially those with fall-off in linear growth and increased MCV, hypothyroidism should be considered in the differential diagnosis of the anemia.