HEMATOLOGY OF HYPOTHYROIDISM

Abstract

In an unselected series of 202 patients with hypothyroidism, anemia was present on diagnosis in 39 of 172 women and 14 of 30 men. Microcytic anemia was present in only 9 patients in the entire series. The average of the mean corpuscular volume (MCV) of all the patients was 90. Fifty-three of 118 patients had normal serum concentrations of vitamin B12, folic acid and Fe. The Hb was low in 13 of these 53 patients and rose on treatment with thyroxine alone. The MCV exceeded 90 fl [femtoliters] in 29 of these 53 patients and in 3 it was greater than 100. The MCV invariably fell on treatment with thyroxine even if the initial value was within the normal range. Of this group of 53 patients, 9 had both anemia and an increased MCV.sbd.the macrocytic anemia of hypothyroidism. A minor degree of anisocytosis of the red blood cells, which was reduced by treatment with thyroxine, was also demonstrated. Acanthocytes were present in the blood films of 32 out of 172 patients but in only 5 did the abnormal cells comprise more than 0.5% of the red cell population. The incidence of new cases of pernicious anemia diagnosed concurrently with the hypothyroidism in the carefully studied group of 118 patients was 8.5%. The MCV of hypothyroid patients with low levels of vitamin B12 was often no greater than in patients with uncomplicated hypothyroidism. The MCV is not a useful discriminant in the diagnosis of pernicious anemia in hypothyroidism. The serum Fe concentration was < 12 .mu.mol/l in 60 out of 118 patients. The total Fe binding capacity of the serum was increased in only 21 of these 60 patients. In 42 hypothyroid patients the low serum Fe concentration was not associated with low levels of either vitamin B12 or folate and of these patients, 22 were anemic. Despite the very low percentage saturation of the Fe binding capacity in all of these patients with a low serum Fe, a lack of Fe did not seem to be the usual determinant of anemia when it occurred.