Shoulder injuries, particularly tendon ruptures, are a common problem affecting individuals across various age groups.

These injuries can severely impact a person’s ability to perform daily activities and significantly reduce their quality of life. While certain factors like age, occupation, and trauma history are often considered as primary causes, hormonal factors have gained significant attention in recent years.

Hormones play a crucial role in maintaining the integrity and strength of tendons, and any imbalance can predispose individuals to tendon ruptures.

1. Estrogen

Estrogen, a primary female sex hormone, plays a vital role in tendon health. It promotes the synthesis of collagen, a key component of tendon structure, and improves the mechanical properties of tendons.

However, reduced estrogen levels during menopause or certain medical conditions can lead to accelerated tendon degeneration and increased risk of rupture. Studies have shown that postmenopausal women are more susceptible to tendon injuries compared to premenopausal women.

2. Androgens

Androgens, primarily testosterone, are male sex hormones, but they also exist in females in smaller amounts. These hormones contribute to tendon strength and have an anabolic effect on tendon tissues.

Low levels of androgens, such as in hypogonadal individuals, have been associated with weakened tendons and elevated risk of rupture. The use of exogenous androgens, such as anabolic steroids, can also disrupt the hormonal balance and lead to tendon damage.

3. Thyroid Hormones

Thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), are responsible for regulating metabolic processes in the body. They also play a role in maintaining tendon health.

Insufficient levels of thyroid hormones can result in reduced collagen synthesis, impair tendon mechanical properties, and increase the likelihood of rupture. Thyroid dysfunction, such as hypothyroidism, has been associated with tendon disorders.

4. Growth Hormone

Growth hormone (GH) is essential for tissue growth, repair, and maintenance. It stimulates the production of collagen and enhances the regenerative capacity of tendons.

Deficiencies in growth hormone can impair the healing process of tendons and predispose individuals to rupture. On the other hand, excess GH levels seen in acromegaly may lead to tendon hypertrophy and increase the risk of tendon ruptures.

5. Glucocorticoids

Glucocorticoids, commonly known as stress hormones, have significant effects on tendon health. They regulate the inflammatory response and modify collagen metabolism.

Prolonged exposure to high levels of glucocorticoids, either due to chronic stress or medication use, can lead to decreased collagen synthesis, impaired tendon healing, and increased vulnerability to tendon ruptures.

6. Insulin-like Growth Factor-1 (IGF-1)

IGF-1 is a hormone with anabolic effects on tissues, including tendons. It promotes collagen synthesis and enhances tendon strength. Reduced levels of IGF-1 have been observed in tendon disorders, suggesting its role in tendon health.

However, more research is needed to fully understand the relationship between IGF-1 and shoulder-tendon ruptures.

7. Parathyroid Hormone

Parathyroid hormone (PTH) regulates calcium metabolism in the body. It also influences the turnover of connective tissues, including tendons. Imbalances in PTH levels, such as hyperparathyroidism, may lead to tendon mineralization and subsequent rupture.

However, further studies are required to explore the exact mechanisms linking PTH to shoulder-tendon ruptures.

8. Insulin Resistance

Insulin resistance, a metabolic disorder associated with reduced response to insulin, can impact tendon health. It disrupts the synthesis of collagen and impairs tendon mechanics.

Conditions like type 2 diabetes, which characteristically involve insulin resistance, have been linked to an increased risk of tendon ruptures. Managing insulin levels and improving insulin sensitivity may help mitigate the risk of these injuries.

9. Cortisol

Cortisol, commonly referred to as the stress hormone, influences tendon health through its anti-inflammatory properties.

However, prolonged exposure to elevated cortisol levels, such as in chronic stress or Cushing’s syndrome, can lead to collagen degradation and reduced tendon strength. This increases the susceptibility to tendon ruptures. Strategies to manage stress and regulate cortisol levels may have a positive impact on tendon health.

10. Melatonin

Melatonin, a hormone regulating sleep-wake cycles, has recently shown potential involvement in tendon health. Studies have suggested that melatonin may have a protective effect on tendons by reducing oxidative stress and inflammation.

Further research is needed to establish a clearer understanding of the relationship between melatonin and shoulder-tendon ruptures.