Age-Related Endocrine Changes - Know All About It

Introduction

The changes that affect the endocrine system can alter the manufacturing, secretion, and catabolism of hormones with age. For instance, with decreased vascularization, the structure of the anterior pituitary gland gets altered, and the content of the connective tissue increases with increasing age. This restructuring can have an impact on the hormonal production of the gland. Since the functions of endocrine organs get altered during the aging process, there is a high prevalence of endocrine malfunction-related disorders in elderly individuals. Age-driven endocrinological changes are an essential and normal component of normal physiology and pathophysiology.

What Are the Common Aging Changes Associated With Hormone Production?

The common aging changes are as follows:

• The endocrine system comprises tissues and organs that manufacture hormones. The naturally occurring chemicals are called hormones and these are manufactured in one location, then released into the bloodstream, and finally used up by other target organs.

• These hormones can entirely control certain target organs while a few organ systems may have their self-internal control systems that operate along with, or instead of, hormones.

• With age, the target tissues turn less sensitive to the hormone that controls them and the amount of production of hormones may also get altered. Blood levels of certain hormones may increase, decrease, or can remain constant. The hormones also get metabolized (broken down) slowly with age.

• A majority of organs that manufacture hormones are controlled by other hormones. Aging also affects this process.

• The hypothalamus which is situated in the brain manufactures hormones that exert control over other structures in the endocrine system, including the pituitary gland. The amount of these regulating hormones tends to remain the same, but the response by the endocrine organs can get altered with aging.

What Are the Various Age-Related Endocrine Changes That Occur in the Body?

The following are the various age-related endocrine changes:

• Menopause: The most notorious age-related endocrine change is the onset of menopause. Estrogens are hormones manufactured by the granulosa interstitial cells, which form the lining of the egg-containing ovarian follicles. Since the ovarian follicles get depleted with age, there is a reduction in the secretion of estrogen, and this reduction in secretion marks the onset of menopause.

In postmenopausal women, the concentration of serum estrogen decreases by at least 80 percent. This decrease in estrogen secretion results in an increase in the secretion and serum concentrations of two hormones namely the luteinizing hormone and the follicle-stimulating hormone. From this, it is evident that the pituitary gland keeps functioning normally in postmenopausal women despite a decline in ovarian function.

• The Testis: The concentrations of serum testosterone decrease very gradually in men starting at around 30 years of age. Men aged 70 years or older may have remarkably lowered testosterone levels. Late-onset hypogonadism (male menopause or andropause) affects about 2 percent of men and usually has an onset at around 40 years of age. This results in testosterone deficiency and decreased testicular function.

Symptoms of late-onset hypogonadism include fatigue, decreased libido, depression, and erectile dysfunction.

This condition can go unnoticed for many years since the symptoms are often minor. The normal age-related decrease in the levels of testosterone in men is due to a reduction in the number of androgen-secreting Leydig cells and is also associated with a progressive decrease in spermatogenesis (sperm cell production), although men mostly remain fertile for many years. Also, a slight compensatory increase in gonadotropin secretion may be observed.

• Thyroid and Adrenal Function: The functioning of the thyroid gland does not get significantly altered with age. The clearance of triiodothyronine and thyroxine decreases to a certain extent but is compensated by a decrease in their production. Hence, the concentrations of triiodothyronine, serum thyroxine, and serum thyrotropin remain unchanged.

Similarly, cortisol (stress response hormone) and ACTH (adrenocorticotropic hormone) production by the adrenal gland does not remarkably change with age, but serum dehydroepiandrosterone (DHEA) concentrations tend to decrease gradually from 30 years of age. The cause of the decrease in DHEA remains unknown. Though the secretion of aldosterone decreases mildly, healthy elderly individuals are able to maintain a normal electrolyte and fluid balance.

• Growth Hormone: The secretion of growth hormone and serum concentrations of IGF (insulin-like growth factor)-1 gradually decreases with age. In comparison to young adults, elderly people have a mild deficiency of IGF-1 and growth hormone. It is due to the deficiency of IGF-1 that decreases muscle mass and increases fat mass in elderly people.

• Vasopressin: Elderly people tend to feel less thirsty in response to water deprivation and have increased basal serum vasopressin (antidiuretic hormone) concentrations. Also, the kidneys in elderly people tend to respond less well to vasopressin when compared with the younger population. These changes elevate the risk of dehydration. On the contrary, if water is available, elevated secretion of vasopressin can lead to an increase in water retention and a decrease in sodium concentrations, resulting in hyponatremia (low levels of sodium in the blood).

• Parathormone: The parathyroid glands are four tiny glands that are situated around the thyroid. The levels of calcium and phosphate are affected by the parathyroid hormone which affects bone strength. The levels of parathyroid hormone increase with age, which may result in osteoporosis (a condition in which the bones tend to become weak and brittle).

• The Pancreatic Islets: The pancreas manufactures the hormone insulin that regulates blood glucose levels. The average fasting blood glucose level tends to increase by 6 to 14 milligrams per deciliter (mg/dL) every 10 years after 50 years of age since the cells turn less sensitive to the effects of insulin. A blood glucose level of 126 mg/dL or higher indicates the presence of diabetes.

What Are the Hormones Whose Levels Are Affected by Age-Related Endocrine Changes?

With age, the levels of certain hormones increase, decrease, or remain constant. Hormones whose levels usually decrease include:

• Calcitonin.

• Renin.

• Growth hormone.

• Aldosterone.

• Estrogen and prolactin levels usually decrease remarkably in women.

Hormones whose levels usually remain constant or only slightly decrease include:

• Cortisol.

• Insulin.

• Epinephrine.

• Thyroid hormones T3 and T4.

• Testosterone levels progressively decrease with age in men.

Hormones whose levels usually increase include:

• Parathyroid hormone.

• Norepinephrine.

• Follicle-stimulating hormone (FSH).

• Luteinizing hormone (LH).

Conclusion

Aging is a natural physiological process in which many physiological functions decline with time. Endocrine functions also get altered due to aging. Having a good knowledge and understanding of endocrine functions in aging will aid in the development of successful lifestyle or pharmacological therapies to treat endocrine-related disorders in elderly patients. With recent advancements and the development of novel endocrine-targeted remedies, an improvement in the quality of life and overall lifespan of individuals can be achieved. Hence, endocrine functions with regard to aging are currently important fields of immense clinical and scientific interest.