Plasma Retinol, Thyroid Stimulating Hormone and Zinc as Predictors of Bone Mineral Density Status

Abstract

Background: Conflicting results on the association between serum retinol level and bone mineral density (BMD) have been published. Thyroid hormones are essential for skeletal development and have direct effect on bone formation and resorption. Bone has one of the highest concentrations of zinc of all tissues, and has been shown to release zinc during deficiency for soft tissue metabolism. Objective: The objective of this study was to assess the relation between plasma levels of retinol, thyroid stimulating hormone (TSH) & zinc and BMD of Egyptian adolescents and adults. Method: The study was a part of a cross sectional national survey conducted by National Nutrition Institute. The sample was a multistage stratified random. Target individuals were classified into two age groups (10- ≤ 18 and 28-≤ 59 years). Bone mineral density and plasma levels of retinol, TSH and zinc were determined. Results: Low and high plasma retinol levels were more prevalent among osteoporotic adolescent and adult males respectively than in normal subjects.. The reverse was observed in adult females. Bone mineral density correlated negatively with plasma retinol level in adult males and females and positively in adolescent males, while among females the association was significant (P = 0.030) and stronger. The highest deficiency of TSH was found among adult and adolescent osteoporotic males, followed by osteopenic adult males and adolescent females. Highly statistically significant difference (P < 0.001) existed between osteoporotic and normal adult males concerning TSH deficiency. The prevalence of zinc deficiency ranged from 5.7% to 9.5% for all target individuals. Plasma Zn levels were correlated negatively with bone mineral density in adult males and females. Conclusion: The results of this study reflects the controversy on the association of plasma retinol and BMD. However, the predominant finding revealed that both low and high plasna retinol levels compromise bone health. Bone status and thyroid function support the adverse effect of hyperthyroidism upon either bone osteoporosis or osteopenia and subsequently upon fracture risk. Plasma zinc deficiency correlated negatively with BMD in adult osteoporotic men.