Hormonal Effects On Bone Health

Introduction:

The endocrine system is a complex network involving glands and organs. Hormones released in the body play an important role in regulating many functions of the body. An imbalance in certain hormones leads to weak bones which are prone to get fractured and broken. Osteopenia (reduction in bone mass) and osteoporosis (weak and porous bones) are the diseased states of bone generally observed.

What Is Bone Health?

Bone is an important organ of humans. It does structural function, helps in movement, gives support, protects the body, and acts as a storehouse for minerals essential for our body.

The bone remodeling (bone turnover) process occurs at the cellular level. Remodeling of bone takes place throughout life. In this process, the adult skeleton is replaced about every 10 years.

Bone health is based on genes and the environment. Errors in genes lead to birth defects whereas environmental factors such as diet and physical activity play a role in bone health in a lifetime. These factors can be changed to have good bone health.

For bone to play its role effectively in the body, it needs good functioning of systemic or circulating hormones. These hormones respond to changes in the levels of calcium and phosphorous in the blood. When there is a deficiency in calcium and phosphorous supply, certain hormones take calcium and phosphorous from bone to do other vital functions of the body. Such withdrawals lead to bone weakening.

What Are the Causes of Bone Disease?

The following are the reasons for bone disease:

• Genetic abnormalities.

• Nutritional deficiencies.

• Hormonal disorders.

• Lack of exercise.

• Immobilization.

• Smoking.

What Are the Hormones That Play a Role in Bone Health?

Hormones respond to changes in blood calcium and phosphorous. These hormones act on bones as well as on kidneys and intestines. Hormones that are related to bone remodeling and supply of calcium and phosphorous are:

Calcium Regulating Hormones:

• Parathyroid.

• Calcitriol (active vitamin D).

• Calcitonin.

Sex Hormones:

• Estrogen.

• Testosterone.

Other Systemic Hormones:

• Growth hormone or insulin-like growth factor.

• Thyroid hormone.

• Cortisol.

How Do Hormones Play a Role in Bone Health?

Many factors like genes, hormones, lifestyle, and local factors play a role in bone mass and health. Peak bone mass reaches in the early 20s. If bones are strong at this age, they are able to cope with the withdrawals of calcium and phosphorous and any changes that occur in bone with aging. Hormones play a vital role in the regulation of calcium thereby influencing bone health.

1. Parathyroid Hormone (PTH): Secretion of PTH occurs in parathyroid glands.

• PTH secretion is increased when calcium levels vary even slightly. PTH acts on the kidney to save calcium and stimulates calcitriol production. Calcitriol increases calcium absorption by the intestine.

• PTH acts on bone and causes the movement of calcium from bone to blood. When there is a small tumor in the parathyroid gland, there is an increased production of PTH takes place causing hyperparathyroidism and this leads to bone loss.

• PTH stimulates bone formation and resorption as well.

• Recent advances have identified a second hormone related to PTH which is a parathyroid hormone-related protein (PTHrP). PTHrP regulates cartilage and bone in the fetus.

• Excessive production of PTHrP occurs in some cancers and acts like PTH causing bone resorption and high calcium levels in the blood, known as hypercalcemia of malignancy.

2. Calcitriol: Calcitriol is a hormone called 1,25 dihydroxy vitamin D formed from vitamin D.

• It increases the absorption of calcium and phosphorous in the intestine thereby supplying minerals to the bone.

• When there is a deficiency of vitamin D, it leads to defective mineralization and bone loss.

3. Calcitonin: This hormone is secreted by the thyroid gland.

• Calcitonin helps maintain bone development and calcium levels in the blood in early life. Its role in adults is not known.

4. Estrogen: Bone growth is increased in children and early in puberty because of estrogen.

• It helps in maintaining calcium levels in the blood, the growth of the skeleton, and the mass and strength of bone. Estrogen also has an effect in stopping the growth in height at the end of puberty.

• Estrogen inhibits bone loss by acting on both osteoclasts and osteoblasts throughout life. As there is a decrease in estrogen during menopause, it may cause bone loss.

5. Testosterone: Testosterone helps in skeletal growth and muscle growth. This leads to increased bone formation because of greater stress on the bone. It is the source of estrogen in the body. Testosterone gets converted to estrogen in fat cells. Estrogen helps maintain bone health.

6. Growth hormone: Regulates skeletal growth. It also acts by stimulating the production of insulin-like growth factor-1 (IGF-1). It is also produced in the bone. Decreased production of growth hormone and IGF-1 in old age leads to the diseased bone.

7. Thyroid hormone: Thyroid hormones increase the energy in bone cells. Deficiency can impair growth in children, excess may lead to bone weakening. Thyrotropin or thyroid stimulating hormone (TSH) may have an effect on bone health.

8. Cortisol: Small amounts of cortisol help in normal bone development but in large amounts, it stops bone growth. Synthetic forms of cortisol given in asthma and arthritis, cause bone loss leading to fracture.

9. Insulin: Insulin helps in bone growth.

10. Leptin: Recent hormone leptin has been shown to have an effect on bone.

How to Diagnose Bone Loss?

To diagnose bone loss following steps are followed:

• Knowing about the family history, particularly osteoporosis.

• Personal medical history.

• Physical examination.

• Bone density test: Bone density is measured using dual-energy X-ray absorptiometry (DEXA).

• DEXA is a painless imaging test using X-rays.

How Can Bone Loss Be Managed?

To improve bone density-

• Treatment with calcium and vitamin D supplements.

• Regular physical exercises.

• Intake of a healthy and balanced diet.

• Hormonal therapy.

How Can Bone Loss Be Prevented?

Following to be adapted to prevent bone loss

• Stop smoking.

• Healthy diet to be followed.

• Exercise regularly.

• Intake of calcium and vitamin D supplements.

• Getting sun exposure helps.

• Avoid alcohol consumption.

• Over a period of time bone density is to be checked.

Conclusion:

Bone health is very important from childhood till the last stage of life. Hormones play an important role in maintaining bone strength and health. In addition to aging, factors such as menopause, medications, liver and kidney diseases, etc can affect bone quality. Hence having a complete knowledge helps one to seek help and get screened to know bone health. Early diagnosis helps in the effective treatment of any condition.