Adrenal steroidogenesis pathway

The human adrenal gland is composed of the cortex and the medulla. The medulla produces bioamines, and the adrenal cortex secretes several classes of steroids (corticosteroids). The adrenal cortex can be considered to be made up of three distinct subunits, each having a characteristic steroid profile. The outermost unit, the zona glomerulosa, produces mineralocorticoids, principally aldosterone (a salt-retaining hormone), which serve to maintain sodium and fluid balance. Glucocorticoids, primarily cortisol, arise from the central zona fasciculata and maintain glucose homeostasis and vascular integrity. The innermost subunit, the zona reticularis, secretes sex steroids (androgens). Disorders of adrenal steroidogenesis may involve overproduction, underproduction, or both the simultaneous overproduction and underproduction of corticosteroids ( Fig. 8-1 ). In this chapter, the following conditions are discussed:

The postperfusion syndrome is an uncommon event following open-heart surgery with extracorporeal circulation. It is associated with a young age at surgery (less than 1 year) and bypass lasting longer than 60 minutes. Luciani et al. (1997) observed the syndrome in an 18-year-old man who underwent transpulmonary patch repair of a ventricular septal defect with cardiopulmonary bypass for 50 minutes. Preoperatively, the patient exhibited a slight gait disorder and unremarkable EEG and laboratory findings. Twelve hours after surgery he developed hypotension and circulatory collapse. This was treated successfully, but 10 days after discharge the patient was admitted with findings suggesting Addison disease. He showed a worsening disturbance of gait, with ataxia and EEG abnormalities. The diagnosis of adrenoleukodystrophy was supported by MRI of the head and confirmed by increased plasma levels of very long chain saturated fatty acids. Thus, Luciani et al. (1997) concluded that this was a case of Addisonian crisis precipitated by surgery in a patient with previously unrecognized AMD.

Catecholamines are produced in chromaffin cells in the medulla of the adrenal gland, from tyrosine , a non-essential amino acid derived from food or produced from phenylalanine in the liver. The enzyme tyrosine hydroxylase converts tyrosine to L-DOPA in the first step of catecholamine synthesis. L-DOPA is then converted to dopamine before it can be turned into noradrenaline. In the cytosol , noradrenaline is converted to epinephrine by the enzyme phenylethanolamine N-methyltransferase (PNMT) and stored in granules. Glucocorticoids produced in the adrenal cortex stimulate the synthesis of catecholamines by increasing the levels of tyrosine hydroxylase and PNMT. [4] [13]

Adrenal steroidogenesis pathway

adrenal steroidogenesis pathway

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