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ple, Cortisol and corticosterone have some mineralocorti-coid activity,- conversely, aldosterone has some glucocorticoid activity. However, given the amounts of these hormones secreted under normal circumstances and their relative activities, glucocorticoids are not physiologically important mineralocorticoids, nor does aldosterone function physiologically as a glucocorticoid.

As discussed in detail later, the amounts of glucocorticoids and aldosterone secreted by an individual can vary greatly from those given in Table 34.1. The amount secreted depends on the person's physiological state. For example, in an individual subjected to severe physical or emotional trauma, the rate of cortisol secretion may be 10 times greater than the resting rate shown in Table 34.1. Certain diseases of the adrenal cortex that involve steroid hormone biosynthesis can significantly increase or decrease the amount of hormones produced.

The adrenal cortex also produces and secretes substantial amounts of androgenic steroids. Dehydroepiandrosterone (DHEA) in both the free form and the sulfated form (DHEAS) is the main androgen secreted by the adrenal cortex of both men and women (see Table 34.1). Lesser amounts of other androgens are also produced. The adrenal cortex is the main source of androgens in the blood in human females. In the human male, however, androgens produced by the testes and adrenal cortex contribute to the male sex hormones circulating in the blood. Adrenal an-drogens normally have little physiological effect other than a role in development before the start of puberty in both girls and boys. This is because the male sex hormone activity of the adrenal androgens is weak. Exceptions occur in individuals who produce inappropriately large amounts of certain adrenal androgens as a result of diseases affecting the pathways of steroid biosynthesis in the adrenal cortex.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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