McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 3 6 Adrenocortical agents

A drenocortical agents are widely used to suppress the immune system. These drugs do not, however, cure any inflammatory disorders. Once widely used to treat a number of chronic problems, adrenocortical agents are now reserved for short-term use to relieve inflammation during acute stages of illness or for replacement therapy to maintain hormone levels when the adrenal glands are not functioning adequately. THE ADRENAL GLANDS The two adrenal glands are flattened bodies that sit on top of each kidney. Each gland is made up of an inner core called the adrenal medulla and an outer shell called the adrenal cortex . The adrenal medulla is actually part of the sympa- thetic nervous system (SNS). It is a ganglion of neurons that releases the neurotransmitters noradrenaline and adrenaline into circulation when the SNS is stimulated. (See Chapter 29 for a review of the sympathetic nervous system.) The secretion of these neurotransmitters directly into the bloodstream allows them to act as hormones, travelling from the adrenal medulla to react with specific receptor sites throughout the body. This is thought to be a backup system for the sympathetic system, adding an extra stimulus to the stress (“fight-or- flight”) response. Diurnal rhythm Research over the years has shown that the adrenocortical hormones are released in a pattern called the diurnal rhythm.The secretion of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol are high in the morning in day-oriented people (those who have a regular cycle of wakefulness during the day and sleep during the night). In such individuals, the peak levels of cortisol usually come between 6 and 8 a.m. The levels then fall off slowly (with periodic spurts) and reach a low in the late evening, with lowest levels around midnight. It is thought that this cycle is related to the effects of sleeping on the hypothalamus, and that the hypothalamus is regulating its stimulation of the anterior pituitary in relation to sleep and activity.The cycle may also be connected to the hypothalamic response to light. This is important to keep in mind when treating people with corticosteroids. In order to mimic the normal diurnal pattern, corticosteroids should be taken immediately on awakening in the morning. Complications to this pattern arise, however, when people work shifts or change their sleeping patterns (e.g. university students). In response, the hypothalamus shifts its release of CRH to correspond to the new cycle. For instance, if a person works all night and goes to bed at The evidence BOX 36.1

The adrenal cortex surrounds the medulla and consists of three layers of cells, each of which synthesises chemically different types of steroid hormones that exert physiological effects throughout the body. The adrenal cortex produces hormones called corticosteroids . There are three types of corticosteroids: androgens, gluco­ corticoids and mineralocorticoids. Androgens are a form of the male sex hormone testosterone. They affect electrolytes, stimulate protein production and decrease protein breakdown. They are used pharmacologically to treat hypogonadism or to increase protein growth and red blood cell production. These hormones are dis- cussed in Chapter 41. Controls The adrenal cortex responds to adrenocorticotropic hormone (ACTH) released from the anterior pituitary. ACTH, in turn, responds to corticotropin-releasing hormone (CRH) released from the hypothalamus. This happens regularly during a normal day in what is called diurnal rhythm (Box 36.1). A person who has a regular cycle of sleep and wakefulness will produce high levels of CRH during sleep, usually around midnight. A resulting peak response of increased ACTH and adrenocortical hormones occurs sometime early in the morning, around 6 to 9 a.m. This high level of hormones then suppresses any further CRH or ACTH release. The corticoster- oids are metabolised and excreted slowly throughout 8 a.m., arising at 3 p.m. to carry on the day’s activities before going to work at 11 p.m., the hypothalamus will release CRH at about 3 p.m. in accordance with the new sleep–wake cycle. It usually takes 2 or 3 days for the hypothalamus to readjust. A person on this schedule who is taking replacement corticosteroids would then need to take them at 3 p.m., or on arising. People who work several different shifts in a single week may not have time to reregulate their hypothalamus, and the corticosteroid cycle may be thrown off. People who have to change their sleep patterns repeatedly often complain about feeling weak, getting sick more easily, or having trouble concentrating. University students frequently develop a pattern of sleeping all day, then staying up all night—a cycle that becomes hard to break as their bodies and endocrine systems try to readjust. It is a challenge to help people understand how the body works and to offer ways to decrease the stress of changing sleep patterns—especially if the health professional is also working several different shifts. Many employers are willing to have employees work several days of the same shift before switching back, mainly because they have noticed an increase in productivity and a decrease in absences when employees have enough time to allow their bodies to adjust to the new shift.