SUN EXPOSURE AND VITAMIN D STATUS AND ITS ASSOCIATION WITH BONE TURNOVER MARKERS IN TRANSFUSIONDEPENDENT ADULT THALASSEMIA PATIENTS

Abstract

INTRODUCTION
Bone disease in patients with thalassemia, encompassing both osteopenia and osteoporosis, is on the rise, partly due to improvements in treatment and survival rates. Bone metabolism in thalassemia is influenced by many confounding factors including hormonal abnormalities, vitamin D deficiency, and iron load from multiple blood transfusions. Bone turnover markers are potentially useful as non-invasive tests to assess bone remodeling in this high-risk population. Due to the increasing frequency of thalassemia bone disease and limited data on vitamin D status among thalassemia patients in countries with adequate sun exposure, this study aimed to assess vitamin D status and its association with sun exposure, bone turnover markers (BTM) and ferritin in adult transfusiondependent thalassemia patients in Malaysia.

METHODOLOGY
This cross-sectional study involved transfusion-dependent thalassemia patients (n = 40) from the adult hematology clinic. All participants had anthropometric measurements, sun exposure index (SI) measured by calculating bodysurface-area x hours of exposure/week, as well as a complete biochemical profile including ferritin, calcium and phosphate levels, 25 hydroxyvitamin(OH)D level, and bone turnover markers serum P1NP and serum CTX as bone formation and bone resorption markers respectively. Vitamin D deficiency was defined as 25-hydroxyvitamin D of less than 75 nmol/L. Vitamin D inadequacy was a combination of vitamin D deficiency and insufficiency.

RESULTS
The study population included 47.5% female and 52.5% male subjects with a mean age of 27.5 ± 5.2 years. Almost all (95%) had elevated serum ferritin (>1000 ug/l) and various endocrinopathies. Increased BTM was detected in 27.5% of patients (n = 11). A high prevalence of vitamin D inadequacy (95%) was observed, with vitamin D insufficiency of 32.5% and deficiency of 62.5%, correlating with ferritin levels (r = -0.444, p = 0.005) and serum P1NP (r = -0.364, p = 0.024). A majority (72.5%) had inadequate sun exposure, particularly among the females (p = 0.021) and Malays (p = 0.003). There was no significant correlation between SI and vitamin D status (r = 0.037, p = 0.824) or BTM.

CONCLUSION
This study revealed a high prevalence of vitamin D inadequacy among adult transfusion-dependent thalassemia patients and low sun exposure among females and Malays. Vitamin D inadequacy was associated with high ferritin and bone formation markers reflecting increased bone remodeling which can lead to higher fracture risk due to bone fragility. Hence, it is important to recognize and treat vitamin D deficiency early in these patients to prevent its deleterious effects on bone health.