Thyroid function in thalassaemia major.

INTRODUCTION: Short stature is common in thalassaemia major. Hypothyroidism resulting from haemosiderosis has been implicated, but this complication has not been investigated in Sri Lanka.

OBJECTIVES: To estimate the thyroid hormone level of patients with thalassaemia major and correlate height with age, iron status and thyroid hormone level.

SETTING: University Unit, Lady Ridgeway Hospital, Colombo.

DESIGN: A cross-sectional comparative study.

METHODS: 33 patients with thalassemia major (19 males) aged 2 years 6 months to 23 years were studied. 21 healthy age and sex matched subjects from the same neighbourhood as the patients served as controls. Anthropometric measurements, skeletal maturity, serum ferritin and thyroid hormone levels were estimated.

RESULTS: The height centiles and height standard deviation scores (SDS) were significantly lower in the patient group. Skeletal maturation was delayed by more than 1 year in 69% of patients. Undernutrition was not seen. The height SDS showed significant reduction with age (r = -0.5, 95% confidence limit -0.72 to -0.18) and with elevated serum ferritin levels (r = -0.8, 95% confidence limit = -0.9 to 0.62). Serum ferritin levels were elevated in the entire patient group with 70% being heavily iron overloaded (serum ferritin > 7000 ng/ml). The thyroxine (T4) levels were within the normal range in all 33 patients. The TSH levels were normal in 32 patients. The patient too had a normal T4 level. The control group had TSH levels comparable with the patients.

CONCLUSION: Hypothyroidism was not present in our iron overloaded thalassaemic patients. The thyroid hormone levels were similar in patients with mild and heavy iron overload. We conclude that routine surveillance for hypothyroidism is unnecessary in thalassaemia major. Other causes for delayed skeletal maturation and short stature need investigation.