Study Looks at Link Between Anemia and Hypothyroidism

Hypothyroidism On Background of Medicaments Composition - Pills, Injections and SyringeAlthough numerous factors can cause anemia, it’s well known that hypothyroidism can cause various types of anemia, including microcytic, macrocytic, and normocytic anemia. Often, the first sign of hypothyroidism in many patients is anemia. It’s also known that thyroid hormones can directly or indirectly stimulate the growth of erythroid colonies through erythropoietin.

In a study, researchers investigated the frequency of anemia, and if it was present, they looked at the etiology of anemia in patients who have hypothyroidism.

Their findings were published online in late December 2011 in the article “Characteristics of anemia in subclinical and overt hypothyroid patients.” The article will appear in an issue of the Endocrine Journal.

A total of 400 patients participated in the study, and these patients were broken out into 3 groups:

  • 100 of the study participants had overt hypothyroidism (overt hypothyroid group)
  • 100 of the participants had subclinical hypothyroidism (subclinical hypothyroid group)
  • 200 of the participants were healthy (control group)

The researchers noted that an overt hypothyroidism diagnosis is confirmed when a patient has elevated thyroid-stimulating hormone (TSH) and low free T4 and/or free T3 levels. In addition, subclinical hypothyroidism is confirmed when a patient has an elevated serum TSH with normal free T4 and free T3 levels.

The Prevalence of Anemia in Patients with Hypothyroidism
The researchers examined peripheral smears of the patients who had anemia.

They found that the frequency of anemia in patients with subclinical hypothyroidism is as high as that in patients with overt hypothyroidism. The prevalence of anemia was 43% in the overt hypothyroid group (p=0.0003) and 39% in the subclinical hypothyroid group (p=0.021). Anemia prevalence was 26% in the control group.

Additionally, the researchers observed that the levels of 3 vitamins and minerals—vitamin B12, iron, and folic acid—were similar between these groups.

They concluded that anemia of chronic disease is the most common type of anemia in patients who have hypothyroidism—whether it’s overt hypothyroidism or subclinical hypothyroidism. They also suggest that hypothyroidism should be suspected in patients who have anemia with an unknown etiology.

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