Page 24 Complete Your CE Test Online - Click Here The thymus The thymus is found below the sternum and contains lymphatic tissue. The thymus, which reaches its maximum size at puberty and then begins to atrophy, secretes the hormones thymosin and thymopoietin. These hormones promote peripheral lymphoid tissue growth [1,3] . Anatomy and physiology alert! The major role of the thymus seems to be related to the immune system since it produces T cells, which are critical to cell-mediated immunity[1] . The pineal gland The pineal gland is located in the middle of the brain at the back of the third ventricle. It produces melatonin, which is believed to regulate circadian rhythms as part of the sleep-wake cycle, body temperature, cardiovascular function, and reproduction[1,2] . Gonads The gonads are the primary source of sex hormones and include the ovaries in females and the testes in males[1,2] . ● ● Ovaries: The ovaries are paired, oval-shaped glands located on either side of the uterus. The ovaries produce eggs (ova) and steroidal hormones estrogen and progesterone. These hormones promote development and maintenance of female sex characteristics, regulate the menstrual cycle, maintain the uterus for pregnancy, and in conjunction with other hormones, prepare the mammary glands for lactation[1,2] . ● ● Testes: The testes are paired structures located in the scrotum in males. The testes produce spermatozoa and the male sex hormone testosterone, which stimulates and maintains male sex characteristics and incites the male sex drive[1,2] . HORMONAL RELEASE MECHANISMS There are four main mechanisms that control the release of hormones [1,2] : Pituitary: Target gland axis The pituitary gland constantly monitors hormone levels. If levels decrease, the pituitary responds by increasing trophic hormones, which trigger their target glands to increase production of specific hormones. Trophic hormones include[1] : ● ● Corticotropin (regulates adrenocortical hormones). ● ● TSH (regulates T3 and T4). ● ● LH (regulates gonadal hormones). If levels are increased, secretion of trophic hormones decreases[1] . Hypothalamic-pituitary-target gland axis The hypothalamus produces trophic hormones that regulate anterior pituitary hormones. Thus, the hypothalamus controls anterior pituitary hormones, which regulate the hormones of their specific target glands [1] . Chemical regulation Endocrine glands that are not controlled by the pituitary gland might be controlled by substances that stimulate gland secretions. An example of chemical regulation is that of blood glucose levels, which regulate glucagon and insulin release[1] . Nervous system regulation The central nervous system (CNS) assists in the hormonal regulation by[1] : ● ● The hypothalamus directly controls the secretion of ADH and oxytocin. ● ● Nervous system stimuli (such as pain, stress, and some drugs) affect ADH levels. ● ● The autonomic nervous system (ANS) controls catecholamine secretion by the adrenal medulla. ● ● Stress stimulates sympathetic stimulation, which, in turn, triggers the pituitary to release corticotrophin. EBP alert! In order to accurately assess the endocrine system nurses must be aware of age-related changes in this system. Research shows that normal age-related changes in the endocrine system include decreased progesterone production, a 50% reduction in serum aldosterone levels, and a 25% decrease in cortisol secretion rate. Also, in stressful situations, an elderly person’s blood glucose level is higher and remains elevated for a longer period of time than that of a younger adult’s[1] . DISEASES AND DISORDERS OF THE ENDOCRINE SYSTEM Arguably, with the exception of diabetes and malignancies of the thyroid, diseases and disorders of the endocrine system are not particularly well understood or even well known by many health care professionals (HCPs). This education program provides information about the pathophysiology, diagnosis, treatment, and nursing considerations of nonmalignant diseases and disorders of the endocrine system. Hypopituitarism Hypopituitarism is a complicated clinical syndrome of deficiency in pituitary hormone production. This can occur when disorders affect the pituitary gland, hypothalamus, or surrounding structures[4] . Partial hypopituitarism and complete hypopituitarism (panhypopituitarism) occur in both adults and children. In children, these conditions may lead to dwarfism and delayed puberty. The prognosis may be good with prompt recognition, appropriate replacement therapy, and correction of underlying causes[1] . Hypopituitarism alert! Panhypopituitarism is characterized by involvement of all pituitary hormones. However, it is more likely that only one or more pituitary hormones are involved. This leads to only isolated or partial hypopituitarism[4] . Pathophysiology Hypopituitarism can impair some or all production of the hormones produced or stored by the pituitary. Here is a review of the hormones associated with the pituitary[1,4] : ● ● The anterior pituitary secretes TSH, FSH, LH, GH, ACTH, and prolactin. ● ● The posterior pituitary stores and secretes two hormones produced by the hypothalamus: vasopressin (ADH) and oxytocin. The hormones of the pituitary target specific glands to stimulate hormones produced and secreted by those glands (e.g., TSH stimulates the thyroid to produce T3 and T4). Therefore, the function of the pituitary is assessed not by measuring pituitary hormones in isolation, but by the functioning of the target glands[4] .