Understanding the impact of Thyroid disorders on the musculoskeletal system

The intricate balance of hormones in our body plays a crucial role in maintaining overall health, and when it comes to thyroid disorders, their influence on the musculoskeletal system cannot be overstated. In a complex interplay of hormones, receptors, and cellular activities, thyroid disorders can significantly affect bone development, mineralization, and muscle function.

At the heart of this physiological symphony are thyroxine and triiodothyronine, collectively known as thyroid hormones. These hormones operate through genomic and extragenomic mechanisms, influencing cellular activities both inside and outside the cell. In the context of bones, the TRα receptor takes centre stage, predominantly found in skeletal cells and acting as a key mediator of triiodothyronine (T3) action.

Understanding the impact of thyroid disorders on bones requires delving into the intricate dance of receptors, particularly TRα1 and TRβ1. These receptors are found in various musculoskeletal components, including chondrocytes, osteoblasts, osteoclasts, bone marrow stromal cells, and the growth plate. TRα1, identified as the primary mediator of T3 action in bones, plays a pivotal role in bone regulation.

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In both hyperthyroid and hypothyroid states in adults, studies have demonstrated impaired bone remodelling and an increased risk of fractures. Thyroid pathologies, though less common in children, can disrupt skeletal maturation, growth, and overall development. Notably, subclinical hyperthyroidism is correlated with low bone mineral density and an elevated risk of fractures.

The impact of thyroid disorders goes beyond bones and extends to muscles. Hyperthyroidism accelerates bone resorption and formation, shortening the remodelling cycle and leading to a negative calcium balance. This imbalance contributes to a decrease in bone mineral density, approximately 12–20%, and untreated hyperthyroidism can result in severe osteoporosis and fractures.

Conversely, hypothyroidism lengthens the bone remodelling cycle, increasing bone mass and mineralization. However, this comes with an elevated risk of fractures due to changes in the quality of bone structure. Additionally, hypothyroidism can lead to hypothyroid myopathy, characterized by poor muscle strength, stiffness, difficulty moving, and fatigue.

The impact of thyroid disorders on the musculoskeletal system is profound and multifaceted. Understanding these intricate connections is essential for effective management, intervention, and overall health. As we unravel the complexities of thyroid function, we gain valuable insights into maintaining the delicate balance that sustains our bones and muscles throughout life.

(Authored byShagun Jain, Senior Physiotherapist and Director of Operations at Healyos Health Care)