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Hakan Cinemre, Cemil Bilir, Feyzi Gokosmanoglu, Talat Bahcebasi, Hematologic Effects of Levothyroxine in Iron-Deficient Subclinical Hypothyroid Patients: A Randomized, Double-Blind, Controlled Study, The Journal of Clinical Endocrinology & Metabolism, Volume 94, Issue 1, 1 January 2009, Pages 151–156, https://doi.org/10.1210/jc.2008-1440
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Abstract
Context: In patients with coexisting iron-deficiency anemia and subclinical hypothyroidism, anemia does not adequately respond to oral iron therapy.
Objective: We studied whether iron-deficiency anemia might indicate treatment of subclinical hypothyroidism.
Design: Patients were assigned to a control or experimental group: 240 mg/d oral iron alone (iron group) or 240 mg/d oral iron plus 75 μg/d levothyroxine (iron/levothyroxine group). Levels of hemoglobin, hematocrit, red blood cell count, serum iron levels, ferritin, total iron-binding capacity, TSH, and free T4 were measured before and after treatment.
Setting: The study was conducted at a university hospital outpatient clinic.
Patients: Fifty-one patients with coexisting iron-deficiency anemia and subclinical hypothyroidism participated in the study.
Intervention: Patients were treated as described above in either the iron group or the iron/levothyroxine group.
Main Outcome Measure: A clinically satisfactory increase in hemoglobin was regarded as successful.
Results: Mean hemoglobin levels increased by 0.4 g/dl in the iron group [95% confidence interval (CI) 0.2–0.7, P = 0.001], whereas it increased by a mean of 1.9 g/dl in the iron/levothyroxine group (95% CI 1.5–2.3, P < 0.0001). The increase in serum iron was greater in the iron/levothyroxine group by a mean of 47.6 μg/dl (95% CI 34.5–60.6, P < 0.0001). Increases in hemoglobin, red blood cells, hematocrit, and serum ferritin levels after treatment were statistically significantly greater in the iron/levothyroxine group (P < 0.0001). Starting hemoglobin and increase in hemoglobin were negatively correlated in the iron/levothyroxine group (r = −0.531, P = 0.006).
Conclusions: Subclinical hypothyroidism should be treated in iron-deficiency anemia patients when both conditions coexist. This would provide a desired therapeutic response to oral iron replacement and prevent ineffective iron therapy.
