C21 steroid hormone

As a mitochondrial P450 system, P450c11 is dependent on two electron transfer proteins, adrenodoxin reductase and adrenodoxin that transfer 2 electrons from NADPH to the P450 for each monooxygenase reaction catalyzed by the enzyme. In most respects this process of electron transfer appears similar to that of P450scc system that catalyzes cholesterol side chain cleavage. [9] Similar to P450scc the process of electrons transfer is leaky leading to superoxide production. The rate of electron leakage during metabolism depends on the functional groups of the steroid substrate. [10]

Blizzard and Kyle (1963) offered the first substantial evidence for the autoimmune concept. They found antiadrenal antibodies in 36 of 71 patients with Addison disease and antithyroid antibodies in 22. Hung et al. (1963) found circulating adrenal antibodies in 2 sibs with Addison disease. A third sib had died from Addison disease. One of the affected sibs also had hypoparathyroidism, pernicious anemia, and superficial moniliasis. The authors suggested the disorder may not be inherited as a simple mendelian recessive but may be autoimmune in nature.

Because steroids are lipophilic, they diffuse easily through the cell membranes, and therefore have a very large distribution volume. In their target tissues, steroids are concentrated by an uptake mechanism which relies on their binding to intracellular proteins (or " receptors ", see below). High concentration of steroids are also found in adipose tissue, although this is not a target for hormone action. In the human male, adipose tissue contains aromatase activity, and seems to be the main source of androgen-derived estrogens found in the circulation. But most of the peripheral metabolism occurs in the liver and to some extent in the kidneys, which are the major sites of hormone inactivation and elimination, or catabolism (see below).

The fetal adrenal cortex lacks expression of the enzyme early on, thus mineralocorticoids (. aldosterone ) and glucocorticoids (. cortisol ) cannot be synthesized. This is significant because cortisol induces type II pneumocytes of the lungs to synthesize and secrete pulmonary surfactant ; without pulmonary surfactant to reduce the alveolar surface tension , premature neonates may die of neonatal respiratory distress syndrome . If delivery is unavoidable (. because of placental abruption , or pre-eclampsia / HELLP syndrome ), then glucocorticoids (. cortisol) can be administered.

C21 steroid hormone

c21 steroid hormone

The fetal adrenal cortex lacks expression of the enzyme early on, thus mineralocorticoids (. aldosterone ) and glucocorticoids (. cortisol ) cannot be synthesized. This is significant because cortisol induces type II pneumocytes of the lungs to synthesize and secrete pulmonary surfactant ; without pulmonary surfactant to reduce the alveolar surface tension , premature neonates may die of neonatal respiratory distress syndrome . If delivery is unavoidable (. because of placental abruption , or pre-eclampsia / HELLP syndrome ), then glucocorticoids (. cortisol) can be administered.

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