Assessment of Thyroid Function in Two Hundred Patients withβ-Thalassemia Major

Abstract

Despite improved hematologic care, multiendocrine dysfunction is a common complication of homozygous transfusion-dependent beta-thalassemia. In this study our goal was to estimate the prevalence of thyroid dysfunction in a large homogenous group of thalassemic patients. Two hundred patients with beta-thalassemia major (100 males and 100 females; mean age, 23.2 +/- 6.7 years; age range 11-43 years), regularly transfused and desferioxamine chelated, were randomly selected from a pool of approximately 800 patients with beta-thalassemia followed in our department. Thyroid function and iron-load status were evaluated by measurements of free thyroxine (FT4), free triiodothyronine (FT3), thyrotropin (TSH), and serum ferritin levels. Of the subgroup of patients who proved to have normal thyroid hormone values, 26 (12 males, 14 females; mean age, 23.6 +/- 6.8 years; age range, 15-36 years) were randomly selected and underwent a standard TRH stimulation test. Thyroid dysfunction was defined as follows: overt hypothyroidism: low FT4 and/or FT3, increased TSH levels; subclinical hypothyroidism: normal FT4, FT3, increased TSH levels; exaggerated TSH response: normal FT4, FT3, normal basal TSH, deltaTSH > or = 21 microIU/mL (TSH levels measured prior and 30 minutes after intravenous TRH administration). Normal thyroid hormone values were found in 167 (83.5%) of the 200 patients studied. Eight (4%) of the remaining patients had overt hypothyroidisim, and 25 (12.5%) had subclinical hypothyroidism. Exaggerated TSH response to TRH was revealed in 7 of the 26 patients with normal hormone values tested (26.9%). Antithyroglobulin and anti-thyroid peroxidase (TPO) antibody titers were negative in 191 patients (95.5%). Mean ferritin levels in hypothyroid and euthyroid patients were 2707.66 +/- 1990.5 mg/L and 2902.9 +/- 1997.3 mg/L, respectively, (p = 0.61), indicating no correlation between ferritin levels and thyroid functional status. Mean ferritin levels in the patients who responded normally to TRH stimulation and in those who overresponded, were 2,586 +/- 1791 mg/L and 3,228 +/- 2473 mg/L, respectively (p = 0.46; NS). Thyroid failure is a rather rare endocrine complication in patients with beta-thalassemic from Greece. In our series, no case of central hypothyroidism was observed. No correlation was found between thyroid functional status and ferritin plasma levels. Approximately 1 of 5 beta-thalassemic patients with normal thyroid hormone values showed an exaggerated TSH response to TRH test. It is to be investigated how many of these patients will establish overt or subclinical hypothyroidism in the future.

Urinary Iodine in Egyptian Patients with Thalassemia Major: A Focus on its Potential Contributing Impact on Consequent Hypothyroidism

“…Comparing patients with a high ferritin level with those with a fair one [less than 1500], there was a highly significant difference in TSH, FT3 and FT4. Similar observations were also noticed by other investigators as Cavallo et al [26] and Filosa et al [3], while Zevras et al [27] and Gathwala et al [28] found that no significant difference in thyroid functions between the well and poorly chelated patients.…”

“…Clinical hypothyroidism has been reported in 5.3% of a thalassemic group and subclinical hypothyroidism in 2.6% in a study of Khan et al [21], while 15% of subclinical hypothyroidism cases were accounted by Zervas et al [22]. A prevalence of 30%, 13.4%, 19.4% and 8.74% have been previously reported by different studies [3,[23][24][25].…”

“…Primary hypothyroidism is characterized by an elevated TSH level and decreased (low) T4. Secondary or central hypothyroidism is characterized by decreased T4 and low TSH [7][8][9][10][11].…”

Prevalence of hypothyroidism, diabetes mellitus and delayed puberty in patients of thalassemia major in a tertiary care center of Jammu province, Jammu Kashmir, India

“…The reason for this could be that in addition to chronic iron overload that results in diabetes, immune system activation against pancreatic beta cells also plays a significant role resulting in impaired insulin secretion. 17 29,30 Again in present study we could not find any relation of hypothyroidism with increasing levels of serum ferritin. There has been consistent occurrence of hypothyroidism in patients of thalassemia but still its causation is poorly understood and there is a lot of variation in its reported prevalence ranging from 4% to 60 %.…”

Effect of Iron Overload on Gonadotrophins and Organ Sex Steroids in Pubertal Thalassemia Patients

“…These findings yield the importance of iron overload in development of endocrine disorders among which hypogonadism is most frequent. In contrast, there are some othereports which have suggested no relation between the level of ferritin and some other endocrinopathies [11,12]. Based on the above mentioned information, we set out to study the effect of iron overload on pituitary gonadotrophins and the gonadal sex steroids in pubertal thalassemics and to conclude whether the former or later is most affected.…”