Hormones and Muscle Mass: How Endocrine Health Supports Strength and Healthy Aging

Maintaining muscle becomes increasingly important as we age, both for metabolic health and for the physical abilities that allow us to remain independent. Skeletal muscle contributes to glucose regulation, mobility, balance, and recovery from illness, while muscular strength helps determine whether ordinary activities remain manageable later in life.

The capacity to maintain and build muscle is influenced by a complex interaction between physical activity, nutrition, recovery, and endocrine signaling. Testosterone, estrogen, growth hormone, insulin, and thyroid hormones participate in different aspects of muscle metabolism, affecting how tissue develops, uses energy, responds to exercise, and repairs itself.

These relationships are of particular interest in longevity medicine because hormonal changes often occur alongside shifts in body composition and physical function. Understanding whether those changes reflect normal aging, altered training demands, inadequate recovery, or an endocrine disorder can help guide appropriate treatment.

At HormoneSynergy®, Dr. Kathryn Retzler considers hormonal health within a broader assessment of muscle, metabolism, bone, cardiovascular health, and physical function. This approach recognizes the opportunities that appropriate hormone treatment may offer while also addressing the other physiological factors involved in maintaining strength.

For additional context, see our Hormone Optimization and Longevity Medicine Guide.

How Hormones Influence Muscle Physiology

Skeletal muscle is continually adapting to the demands placed upon it. Muscle proteins are synthesized and broken down throughout the day, with the balance influenced by exercise, nutrient availability, illness, and hormonal signaling.

Resistance exercise stimulates pathways involved in muscle protein synthesis and remodeling. Adequate dietary protein supplies the amino acids needed for those processes, while sufficient energy intake supports recovery and adaptation.

Hormones help regulate the biological environment in which these changes occur. Testosterone influences androgen-sensitive processes involved in muscle development. Insulin participates in nutrient metabolism and helps restrain protein breakdown. Thyroid hormones affect cellular energy turnover, while growth hormone and insulin-like growth factor 1 contribute to tissue growth and metabolic regulation.

Estrogen also has important effects in skeletal muscle and connective tissues, particularly in relation to muscle function, recovery, and the physiological changes associated with menopause.

These pathways operate together, although each has a different role. Their interactions help explain why muscle maintenance may become more difficult during periods of illness, inadequate nutrition, endocrine dysfunction, or reduced physical activity.

Testosterone and Muscle Development

Testosterone is among the most extensively studied hormones involved in skeletal muscle development. It acts through androgen receptors and influences processes associated with muscle protein synthesis, tissue growth, and body composition.

In men, clinically significant testosterone deficiency may be accompanied by reduced lean mass, increased adiposity, diminished sexual function, and other symptoms. Some men also experience reduced energy or physical performance, although those complaints can have multiple contributing causes.

Clinical studies have demonstrated that testosterone replacement in appropriately diagnosed men can increase lean body mass and improve certain measures of muscular function. The extent of improvement depends on the patient, treatment, and accompanying physical activity. Increased lean mass does not always produce equivalent gains in strength.

Testosterone is also present and physiologically active in women, although circulating concentrations are substantially lower. Its contributions to female musculoskeletal health remain an area of research, particularly during aging and hormonal transitions.

The clinical indications for testosterone therapy differ between men and women. In women, current evidence supports its use primarily for carefully assessed hypoactive sexual desire disorder in appropriate patients rather than routine muscle enhancement.

For men with confirmed testosterone deficiency, treatment may complement resistance training and nutrition within a broader plan to improve physical health. Assessment typically includes symptoms, repeated testosterone measurements, and consideration of LH, FSH, sex hormone-binding globulin, and other relevant findings.

At HormoneSynergy®, testosterone treatment is considered within comprehensive care, allowing changes in strength, body composition, metabolic health, and symptoms to be evaluated together.

Estrogen and Musculoskeletal Health

Estrogen is widely recognized for its importance in reproductive physiology and bone health, but its biological effects also extend to skeletal muscle, connective tissue, and metabolic regulation.

Estrogen receptors are present in muscle tissue, where estrogen signaling appears to participate in processes involving muscle repair, inflammation, mitochondrial activity, and aspects of muscle function.

During perimenopause and menopause, declining ovarian hormone production occurs alongside changes in body composition and musculoskeletal health. Women may experience increasing abdominal adiposity, changes in recovery, and gradual reductions in muscle strength as they grow older.

These changes are not caused exclusively by declining estrogen. Physical activity, nutrition, chronological aging, sleep, and other factors also influence muscle health during midlife.

Research investigating menopausal hormone therapy and skeletal muscle has produced interesting findings, although results have varied. Some studies suggest beneficial effects on particular measures of muscle function or composition, while others demonstrate limited or inconsistent improvements.

Menopausal hormone therapy has established benefits for vasomotor symptoms and prevention of bone loss in appropriately selected women. Improvements in sleep and daily functioning may also help women maintain regular physical activity, which can support muscular health indirectly.

The relationship between estrogen, exercise adaptation, and muscle aging remains an important area of investigation, particularly as researchers seek to understand how women's musculoskeletal health can be better supported across the menopausal transition.

Growth Hormone, IGF-1, and Tissue Repair

Growth hormone is produced by the pituitary gland and influences metabolism, tissue growth, and body composition. Many of its growth-related effects are mediated through insulin-like growth factor 1, commonly called IGF-1.

Growth hormone secretion changes throughout life and generally declines with age. Its release is influenced by sleep, nutritional status, exercise, body composition, and other physiological factors.

In people with established growth hormone deficiency, appropriate replacement therapy can improve certain aspects of body composition and other clinical outcomes. Diagnosis requires careful endocrine evaluation because growth hormone secretion is pulsatile and cannot be interpreted reliably from a random measurement alone.

There is considerable scientific interest in the relationships among growth hormone, IGF-1, tissue maintenance, and aging. These pathways influence cellular growth and repair, but they also participate in biological processes that are considerably more complex than the simple assumption that higher growth hormone concentrations produce healthier aging.

For otherwise healthy older adults, growth hormone treatment has not demonstrated sufficient benefits to justify routine use as an anti-aging intervention, and adverse effects may include fluid retention, joint discomfort, and impaired glucose regulation.

At HormoneSynergy®, growth hormone physiology is considered when clinically relevant, while preserving muscle is primarily supported through established exercise, nutrition, and appropriate medical treatment. The clinic does not prescribe growth hormone for anti-aging purposes.

Insulin, Nutrient Availability, and Muscle Metabolism

Insulin plays an important role in muscle metabolism because skeletal muscle is one of the body's principal sites of glucose disposal.

Following a meal, insulin helps regulate circulating glucose and facilitates its storage and utilization. Muscle contraction also promotes glucose uptake through mechanisms that are partly independent of insulin, contributing to the metabolic benefits of physical activity.

Insulin has additional effects on protein metabolism, particularly through its ability to reduce protein breakdown when adequate amino acids are available.

Insulin resistance can interfere with normal glucose regulation and frequently occurs alongside excess visceral fat, physical inactivity, and other cardiometabolic risk factors. These conditions may also contribute to changes in muscle quality and physical function.

Resistance training and aerobic exercise can improve insulin sensitivity, while maintaining sufficient muscle supports the body's capacity to utilize glucose.

This relationship helps explain why preserving muscle is relevant to metabolic health even when a person is not interested in athletic performance or muscular size.

For a broader clinical discussion, see Metabolic Syndrome and Cardiometabolic Risk.

Thyroid Hormones and Muscle Function

Thyroid hormones help regulate cellular metabolism, energy expenditure, and numerous processes required for normal muscle function.

Both insufficient and excessive thyroid hormone activity can affect skeletal muscle. Hypothyroidism may contribute to fatigue, muscle discomfort, weakness, and reduced exercise tolerance. Hyperthyroidism can increase protein turnover and, when substantial or prolonged, contribute to muscle wasting and weakness.

Appropriate treatment of thyroid disease can improve muscular symptoms and help restore normal metabolic function, although recovery depends on the severity and duration of the disorder.

Thyroid evaluation may therefore be important when a patient develops unexplained weakness, fatigue, changes in body composition, or reduced physical performance accompanied by other suggestive symptoms.

The objective is to restore appropriate thyroid function rather than to manipulate thyroid hormone concentrations for weight loss or enhanced exercise performance.

Cortisol, Stress, and Muscle Recovery

Cortisol is another hormone involved in muscle and energy metabolism. Produced by the adrenal glands, cortisol helps regulate glucose availability, inflammatory responses, and the body's adaptation to physiological stress.

Normal cortisol secretion is essential to health and follows a daily rhythm influenced by sleep and circadian regulation.

Prolonged exposure to excessive glucocorticoid activity, whether from conditions such as Cushing syndrome or certain medications, can contribute to muscle wasting and weakness. This reflects the effects of excessive glucocorticoid signaling rather than the ordinary fluctuations associated with daily stress.

Sleep, nutrition, and appropriate recovery remain important for sustaining physical activity and muscular adaptation. When symptoms suggest a recognized endocrine disorder, targeted evaluation can help determine whether abnormal cortisol physiology is contributing.

Hormones and the Response to Resistance Training

Resistance training produces muscular adaptation through mechanical loading and activation of intracellular signaling pathways involved in tissue remodeling.

Hormones influence this process, but the temporary increases in testosterone, growth hormone, or other circulating hormones that may occur after exercise are not necessarily reliable indicators of subsequent muscle growth.

Training quality, progressive overload, adequate nutrition, and recovery are more useful practical considerations when developing an exercise program.

Muscle remains responsive to training throughout adulthood. Research involving older adults demonstrates that progressive resistance exercise can improve strength and physical function, including among people who have already experienced clinically meaningful muscle decline.

These findings are encouraging because they show that aging does not eliminate the capacity to improve muscular performance. Hormonal health may influence individual responses, but physical adaptation remains possible across a wide range of ages.

Learn more in Resistance Training and Longevity.

Muscle Loss With Aging and the Role of Endocrine Health

Age-related muscle decline is influenced by several interacting processes, including changes in activity, nutritional intake, neurological function, chronic disease, and endocrine signaling.

Sarcopenia describes a progressive skeletal muscle disorder associated with reduced strength and muscle quantity or quality. Contemporary clinical approaches place particular emphasis on muscle strength because it is closely related to physical performance and independence.

Hormonal changes can contribute to this process, although they are rarely the only explanation. An older adult experiencing reduced strength may benefit from assessment of exercise habits, protein intake, medications, metabolic health, and relevant endocrine conditions.

Where hormonal deficiency or disease is identified, appropriate treatment may help address contributing symptoms or physiological abnormalities. Resistance training and nutrition remain valuable regardless of whether hormone treatment is needed.

Early recognition creates opportunities to improve strength and function before substantial disability develops.

For further reading, see Sarcopenia Explained: Age-Related Muscle Loss and Muscle Mass and Longevity.

Evaluating Muscle Health in Longevity Medicine

Changes in muscle mass and strength are best evaluated through a combination of clinical history, physical performance, body composition measurements, and selected laboratory testing.

DEXA can estimate regional lean tissue, fat mass, and bone mineral density, while SECA bioelectrical impedance analysis provides additional body composition estimates that may be useful for ongoing monitoring.

Lean mass measurements are valuable, although they do not directly measure every aspect of muscle quality or function. Strength testing, walking speed, chair-rise performance, and other functional assessments provide complementary information when clinically appropriate.

Hormonal testing can help identify endocrine disorders that may contribute to weakness or changes in body composition. The choice of tests depends on symptoms, medical history, examination findings, and the suspected condition.

At HormoneSynergy®, Dr. Kathryn Retzler evaluates hormonal concerns within the Optimal Aging Assessment alongside advanced laboratory testing, DEXA, SECA, cardiovascular assessment, and other relevant health measurements.

This broader approach can help identify whether the most useful intervention involves resistance training, nutritional changes, treatment of a hormonal disorder, metabolic management, or a combination of strategies.

Preserving Muscle Through Midlife and Beyond

The growing understanding of muscle physiology offers considerable opportunities for preventive medicine. Resistance training can improve strength in older adults, nutrition can support muscle protein synthesis, and appropriate medical treatment can address disorders that interfere with physical function.

Creatine monohydrate may also support muscular strength and training adaptations in selected individuals, particularly when combined with resistance exercise. Research continues into other interventions that may influence muscle metabolism, mitochondrial function, and age-related changes in muscle tissue.

Hormonal health remains an important part of this work because endocrine signaling influences how muscle responds to its physiological environment. Identifying genuine hormonal abnormalities can improve the precision of treatment and may offer benefits for symptoms, body composition, or other established clinical outcomes.

Maintaining muscle strength supports the ability to remain active, recover from setbacks, and preserve independence with age. The combination of exercise, nutrition, appropriate medical care, and objective monitoring provides a practical foundation for protecting that capacity.

Related HormoneSynergy® Resources

• Hormone Optimization and Longevity Medicine
• Muscle Mass and Longevity: Why Strength Predicts Healthspan
• Muscle Mass and Longevity: Strength, Metabolism, and Healthy Aging
• Resistance Training and Longevity
• Sarcopenia and Age-Related Muscle Loss
• Metabolic Syndrome and Cardiometabolic Risk
• Optimal Aging Assessment

Clinical References

1. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018. Read guideline.
2. Cruz-Jentoft AJ, Bahat G, Bauer J, et al. Sarcopenia: Revised European Consensus on Definition and Diagnosis. Age and Ageing. 2019. Read consensus.
3. Endocrine Society. Evaluation and Treatment of Adult Growth Hormone Deficiency. Clinical Practice Guideline. Read guideline.
4. The North American Menopause Society Advisory Panel. The 2022 Hormone Therapy Position Statement. Menopause. 2022. Read position statement.

Frequently Asked Questions

Which hormones influence muscle mass?

Testosterone, estrogen, growth hormone, IGF-1, insulin, thyroid hormones, and cortisol all influence different aspects of skeletal muscle physiology, including protein metabolism, energy utilization, and tissue maintenance.

Can hormone therapy improve muscle mass?

Appropriate treatment of certain endocrine disorders can improve body composition or specific muscular outcomes. Testosterone replacement in men with established deficiency, for example, can increase lean mass. Benefits depend on the condition, treatment, and accompanying physical activity.

How does estrogen influence muscle health?

Estrogen participates in muscle and connective tissue physiology. Research is examining its influence on muscle function, repair, and changes associated with menopause. Exercise and nutrition remain important for muscle preservation.

Why is muscle important for metabolic health?

Skeletal muscle is a major site of glucose disposal and contributes to insulin sensitivity. Regular resistance and aerobic exercise help improve glucose regulation and maintain physical function.

Does growth hormone help maintain muscle with age?

Growth hormone and IGF-1 participate in tissue growth and metabolism. Replacement may be beneficial for patients with established growth hormone deficiency, but growth hormone therapy is not recommended for routine anti-aging use in otherwise healthy adults.

Can thyroid disorders cause muscle weakness?

Yes. Both hypothyroidism and hyperthyroidism can affect muscle metabolism and physical function. Appropriate diagnosis and treatment may improve muscular symptoms.

Can older adults improve muscle strength?

Yes. Progressive resistance training can improve strength and physical performance throughout much of adulthood, including in people who have already experienced age-related muscle decline.

How can hormonal and muscle health be evaluated together?

A comprehensive assessment may include symptom history, relevant hormonal laboratory testing, DEXA or SECA body composition measurements, metabolic markers, and evaluation of strength or physical performance.

Medical Disclaimer: This article is intended for educational purposes and does not replace individualized medical advice. Hormonal testing, treatment, nutritional supplementation, and exercise recommendations should be based on individual medical circumstances.