Endocrine Overview (38 CFR 4.119)

The endocrine system consists of glands and other structures that produce secretions that are discharged into the blood and lymph, circulated to various parts of the body, ultimately affecting metabolism and other vital body functions. The pituitary gland (hypophysis), thyroid gland, parathyroid glands, adrenal glands (suprarenal), islets of Langerhans of the pancreas, gonads (ovaries and testes), pineal body, and hypothalmus are components of the endocrine system. Major conditions involving the pituitary gland, the thyroid gland, the parathyroid glands, the adrenal glands, and the islets of Langerhans are included in this rating schedule section. In terms of gonads, conditions related to the female reproductive tract are in the section entitled, gynecological conditions and disorders of the breast, and conditions related to the male reproductive tract are in the section entitled, genitourinary system. Although the endocrine system consists of separate entities, the parts are intimately interrelated and work together.

Major constituents of the endocrine system are glands, hormones, and receptors. The glands (endocrine structures) are secretory structures with specialized cells and no passageways to conduct secretions from the structures. The key elements are the hormones, which serve as chemical messengers. Hormonal action involves the passage of hormones to target sites, and the bonding of hormones to specific receptor cells.

The location and overall function of the principal endocrine glands included in this section are described below:

• The pituitary gland is located in the sphenoid bone at the base of the brain, consisting of two regions; the anterior and posterior lobes. The hormones regulate growth, reproduction, and various metabolic activities.

• The thyroid gland is located in the anterior portion of the neck, consisting of two lobes. The hormone regulates metabolic rate, and, indirectly, affects nutrition and growth.

• The parathyroid glands are situated at the back of the thyroid gland, consisting of four or five small glands. The hormone regulates calcium and phosphorus metabolism and, indirectly, affects muscle irritability.

• The adrenal glands, consisting of two glands with a gland on top of each kidney, are involved with separate functions. The outer portion (cortex) of each gland regulates carbohydrate and fat metabolism, and salt and water balance. Most of the body systems are affected by the action of hormones from the cortex. The inner portion (medulla) of each gland manufactures and stores substances that are directly related to the adjustment of the body during stress and emotional changes.

• The islets of Langerhans are clusters of cells located in the pancreas. The pancreas is located behind and slightly below the stomach. The secretions (insulin and glucagon) regulate blood sugar level.

Endocrine