Characterization of the anaemia associated with Graves' disease

Abstract

Background: Graves' disease (GD) is associated with hyperthyroidism. Thyrotoxicosis adversely affects multiple organ systems including haematopoiesis. Anaemia occurring specifically in GD has not been systematically studied previously.

Objective: To define the prevalence and characteristics of the anaemia associated with GD.

Design: Eighty-seven newly diagnosed patients with GD were recruited. Haematological indices, thyroid function and inflammatory parameters were examined at presentation and following successful treatment of hyperthyroidism.

Setting: Tertiary care academic referral centre.

Results: Thirty-three per cent of subjects presented with anaemia. The prevalence of anaemia not attributable to other causes (GD anaemia) was 22%. GD anaemia affected 41.6% (10/24) of men compared to 17.5% of women (11/63). Mean erythropoietin (EPO) levels (15.5 +/- 5.3 mIU/ml) were within normal reference limits but significantly higher (P = 0.004) than those of the non-anaemic controls. Hgb correlated inversely with EPO (P = 0.05) and CRP (P = 0.04) levels, a relationship that persisted after multivariate adjustment for TT3 or TT4. With antithyroid therapy for 16 +/- 6.3 weeks, Hgb levels normalized in 8 out of 9 subjects with GD anaemia (10.7 +/- 0.8 to 13.5 +/- 1.3 g/dl, P = 0.0001). After normalization of Hgb, mean MCV and TIBC were significantly increased, and median ferritin and mean EPO were significantly decreased.

Conclusions: GD anaemia is common, resembles the anaemia of chronic disease, and is associated with markers of inflammation. It corrects promptly with return to the euthyroid state following treatment.

Fig 1. Correlation between Hgb and TT4, TT3 and CRP levels at presentation

Scatter plot 1A displays the Pearson correlation (Spearman correlation= -0.19, P=0.12) between Hgb and TT4 levels [T3 in insert] in GD anemic (◇) and non-anemic (■) subjects. The Pearson correlation between Hgb and CRP levels in these subjects is displayed in scatter plot 1B. [Spearman correlation= -0.38, P=.002].

Fig 2. Correlation between changes in Hgb and TT4, TT3 and CRP levels following successful therapy

Scatter plot 2A displays the Pearson correlation (Spearman correlation= -0.42, P=0.02) between change (delta) in Hgb and TT4 levels [T3 in insert] of GD anemic (◇) and non-anemic (■) subjects. Scatter plot B displays the Pearson correlation (Spearman correlation= 0.25, P=0.20) between change (delta) in Hgb and CRP levels in these subjects.

Fig 3. Hgb levels correlate inversely with thyroid hormone levels

Panel A and B contain data from two newly diagnosed subjects presenting with GD anemia. The Hgb and TT3 levels are plotted along the ordinate and time (weeks) along the abscissa. TT3 levels fluctuated widely in these subjects as a consequence of intermittent compliance and were mirrored by coincident changes in Hgb.