Conversion of pregnenolone to progesterone is mediated by 3β-hydroxysteroid dehydrogenase. Pregnenolone exits the mitochondria and is converted to either progesterone or 17α-OH-pregnenolone. The line denotes which steps occur outside the adrenal glands.Ĭells of the adrenal zona fasciculata and zona reticularis synthesize and secrete the glucocorticoids cortisol or corticosterone through the following pathway (see Figure 6–3).

The zona glomerulosa possesses aldosterone synthase activity, and this enzyme converts deoxycorticosterone to corticosterone, corticosterone to 18-hydroxycorticosterone, and 18-hydroxycorticosterone to aldosterone, the principal mineralocorticoid produced by the adrenal glands. Therefore, pregnenolone can be converted only into progesterone. Cells in the zona glomerulosa do not have 17α-hydroxylase activity. Both 17α-OH-pregnenolone and 17α-OH-progesterone can be converted to the androgens dehydroepiandrosterone (DHEA) and androstenedione, respectively. In addition, 17α-OH-progesterone can be converted to androstenedione. Thereafter, 17α-OH-pregnenolone is converted to 17α-OH-progesterone by 3β-hydroxysteroid dehydrogenase, 17α-OH-progesterone is converted to 11-deoxycortisol by the enzyme 21-hydroxylase, and 11-deoxycortisol is converted to cortisol by 11β-hydroxylase. Pregnenolone is converted to progesterone by 3β-hydroxysteroid dehydrogenase or to 17α-OH-pregnenolone by 17α-hydroxylase. Cholesterol is converted to pregnenolone by the cytochrome P450 side-chain cleavage enzyme. Identify diseases caused by oversecretion of adrenal catecholamines.Īdrenal steroid hormone synthetic pathway.

Describe and integrate the interactions of adrenal medullary and cortical hormones in response to stress.Describe the biologic consequences of sympatho-adrenal medulla activation and identify the target organs or tissues for catecholamine effects along with the receptor types that mediate their actions.Identify the chemical nature of catecholamines and their biosynthesis and metabolic fate.Identify the causes and consequences of oversecretion and undersecretion of glucocorticoids, mineralocorticoids, and adrenal androgens.Describe the regulation of mineralocorticoid secretion and relate this to the regulation of sodium and potassium excretion.Identify the major mineralocorticoids, their biologic actions, and their target organs or tissues.Understand the cellular mechanism of action of adrenal cortical hormones and identify their major physiologic actions, particularly during injury and stress.Describe and contrast the regulation of synthesis and release of the adrenal steroid hormones (glucocorticoids, mineralocorticoids, and androgens) and the consequences of abnormalities in their biosynthetic pathways.Identify the functional anatomy and zones of the adrenal glands and the principal hormones secreted from each zone.

Adrenal hormones