Longitudinal study on thyroid function in patients with thalassemia major

Primary hypothyroidism is one of the most frequent complications observed in patients suffering from thalassemia. We investigated thyroid function in a group of patients attending the Pediatric Department of Cardarelli Hospital in order to determine in how many patients thyroid function worsened during a 12 year-period of follow up.

Fifty patients with beta-thalassemia major (27 females and 23 males), mean age 25.7+/-1.4 years, were re-evaluated according to the criteria of Faglia et al. Thyroid dysfunction was defined as follows: overt hypothyroidism (low FT4 and increased TSH levels >10 microU/ml); compensated hypothyroidism (normal FT4, TSH 5-10 microU/ml, and abnormal TRH test); subclinical hypothyroidism (normal FT4, basal TSH 0-5 microU/ml, abnormal TRH test). Correlation with hematological, biochemical and growth parameters was evaluated.

Ten out of 50 patients evaluated in a previous study had moved to other centers, and four patients had died from cardiac problems. Thus, 36 patients completed a 12 year-period of follow-up. In 25% of the patients the degree of thyroid dysfunction worsened with different degrees of severity. The prevalence of overt hypothyroidism had risen to 13.9% from 8.4%. No cases of secondary hypothyroidism were observed, and anti-thyroglobulin and anti-thyroperoxidase (TPO) antibody titers were negative in all patients. Five (28%) out of 17 patients with normal thyroid function previously (one female, four male) showed an exaggerated TSH response to a TRH test, with normal serum levels of FT4, and they were classified as having subclinical hypothyroidism; while another patient died of cardiac complications. Four out of twelve patients with previous subclinical hypothyroidism showed worsening with a different degree of severity: two females changed to compensated hypothyroidism, and two males to overt hypothyroidism. Furthermore, two out of six patients with compensated hypothyroidism and one out of four patients with overt hypothyroidism died of cardiac failure. In all patients there was no correlation between serum ferritin levels, blood transfusion, pretransfusion Hb levels and worsening of thyroid function. Echographic data showed features of dishomogeneity of the parenchyma with different degrees of severity in accordance with the criteria of Sostre and Reyes. The highest score was observed in all patients with overt and compensated hypothyroidism.

A slow worsening of thyroid function was observed in 25% of the studied patients and only two of them developed overt hypothyroidism. The echographic pattern seems to be strongly predictive of thyroid dysfunction.