Factors that Affect Endocrine Function
Susan Kirk, MD
Dorothy Shulman, MD
Bradley D. Anawalt, MD
Everyone's body undergoes changes, some natural and some not, that can affect the way the endocrine system works. Some of the factors that affect endocrine organs include aging, certain diseases and conditions, stress, the environment, and genetics.
Despite age-related changes, the endocrine system functions well in most older people. However, some changes occur because of damage to cells during the aging process and genetically programmed cellular changes. These changes may alter the following:
- hormone production and secretion
- hormone metabolism (how quickly hormones are broken down and leave the body)
- hormone levels circulating in blood
- target cell or target tissue response to hormones
- rhythms in the body, such as the menstrual cycle
For example, increasing age is thought to be related to the development of type 2 diabetes, especially in people who might be at risk for this disorder. The aging process affects nearly every gland. With increasing age, the pituitary gland can become smaller and may not work as well. For example, production of growth hormone might decrease. Decreased growth hormone levels in older people might lead to problems such as decreased lean muscle, decreased heart function, and osteoporosis. Aging affects a woman's ovaries and results in menopause, usually between 50 and 55 years of age. In menopause, the ovaries stop making estrogen and progesterone and no longer have a store of eggs. When this happens, menstrual periods stop.
Diseases and Conditions
Chronic diseases and other conditions may affect endocrine system function in several ways. After hormones produce their effects at their target organs, they are broken down (metabolized) into inactive molecules. The liver and kidneys are the main organs that break down hormones. The ability of the body to break down hormones may be decreased in people who have chronic heart, liver, or kidney disease.
Abnormal endocrine function can result from:
- congenital (birth) or genetic defects (see section on Genetics below)
- surgery, radiation, or some cancer treatments
- traumatic injuries
- cancerous and non-cancerous tumors
- autoimmune destruction (when the immune system turns against the body's own organs and causes damage)
In general, abnormal endocrine function creates a hormone imbalance typified by too much or too little of a hormone. The underlying problem might be due to and endocrine gland making too much or too little of the hormone, or to a problem breaking down the hormone.
Physical or mental stressors can trigger a stress response. The stress response is complex and can influence heart, kidney, liver, and endocrine system function. Many factors can start the stress response, but physical stressors are most important. In order for the body to respond to, and cope with, physical stress, the adrenal glands make more cortisol. If the adrenal glands do not respond, this can be a life-threatening problem. Some medically important factors causing a stress response are
- trauma (severe injury) of any type
- severe illness or infection
- intense heat or cold
- surgical procedures
- serious diseases
- allergic reactions
Other types of stress include emotional, social, or economic, but these usually do not require the body to produce high levels of cortisol in order to survive the stress.
An environmental endocrine disrupting chemical (EDC) is a substance outside of the body that may interfere with the normal function of the endocrine system. Some EDCs mimic natural hormone binding at the target cell receptor. (Binding occurs when a hormone attaches to a cell receptor, a part of the cell designed to respond to that particular hormone.) EDCs can start the same processes that the natural hormone would start. Other EDCs block normal hormone binding and thereby prevent the effects of the natural hormones. Still other EDCs can directly interfere with the production, storage, release, transport, or elimination of natural hormones in the body. This can greatly affect the function of certain body systems.
EDCs can affect people in many ways:
- disrupted sexual development
- decreased fertility
- birth defects
- reduced immune response
- neurological and behavioral changes, including reduced ability to handle stress
Your endocrine system can be affected by genes. Genes are units of hereditary information passed from parent to child. Genes are contained in chromosomes. The normal number of chromosomes is 46 (23 pairs). Sometimes extra, missing, or damaged chromosomes can result in diseases or conditions that affect hormone production or function. The 23rd pair, for example, is the sex chromosome pair. A mother and father each contribute a sex chromosome to the child. Girls usually have two X chromosomes while boys have one X and one Y chromosome. Sometimes, however, a chromosome or piece of a chromosome may be missing. In Turner syndrome, only one normal X chromosome is present and this can cause poor growth and a problem with how the ovaries function. In another example, a child with Prader-Willi syndrome may be missing all or part of chromosome 15, which affects growth, metabolism, and puberty. Your genes also may place you at increased risk for certain diseases, such as breast cancer. Women who have inherited mutations in the BRCA1 or BRCA2 gene face a much higher risk of developing breast cancer and ovarian cancer compared with the general population.