Adrenal Gland Hormones : Functions, Symptoms and Disorders

Adrenal glands are also called as glands of emergency as they secrete most vital hormones needed during an emergency. The cortex part( Outer zone) of the adrenal gland makes up to 80-90% of the gland and is a source of cortisol hormone. The medulla part (inner zone) makes up to 10-20%of the adrenal gland and is a source of the catecholamine hormone.

Adrenal Gland Hormones

• Hormones secreted by adrenal cortex are called as corticosteroids can be grouped as :

1. Glucocorticoids - It includes cortisol and corticosterone which have a widespread effect on glucose and protien metabolism.
2.  Mineralocorticoids - Aldosterone is the main corticosteroid . It regulates the sodium balance and extracellular fluid volume in the body.
3. Adrenal Sex steroids - These include androgenic substances such as dehydroepiandrostenedione (DHEA).
4. In addition it also secretes biosynthetic precursors of three end products - Progesterone, 11 deoxycorticosterone and 11-doxycortisol.

• Hormones secreted by adrenal medulla are called as catecholamines which include-

1. Epinephrine
2. Nor-epinephrine
3. Dopamine

Also Read: Hemostasis: Stages, Steps and Clinical Applications

Adrenal Hormones Functions

Function of Aldosterone

• Sodium reabsorption into the renal tubular epithelial cells.
• Potassium excretion in the kidney due to active reabsorption of Na+ in exchange of K+ and H+.
• On sweat glands, it decreases the loss of sodium and chloride in sweat and salivary secretion.
• Enhances sodium absorption from the colon.

Function of Catecholamines

• Metabolic effects like increase in oxygen consumption and increase CO2 output.
• Raise BMR
• Increase heat production due to stimulation of cellular oxidative processes.
• Causes hyperglycemia by carbohydrate metabolism.
• Stimulates glucagon secretion and inhibits the insulin secretion.
• Increases lipolysis in adipose tissue and muscle
• Increase Heart rate by action on SA node.
• In GIT, It decreases tone and motility of smooth muscles of wall of gut and contracts the sphincter of the gut causing constipation.
• Dilation of pupil

Function of Glucocorticoids

• Metabolic effects like increase in gluconeogenesis 
• Decrease utilization of glucose in the peripheral tissues .
• Inhibits de novo protien synthesis
• Lipolysis
• Mild mineralocorticoid activity.

Also Read: Synapse: Components, Types and Function

Adrenal Hormones Synthesis

1. Glucocorticoids - Glucocorticoids are synthesized largely by the cells forming the zona fasciculata. They are synthesized from cholesterol which is actively taken by the adrenal gland from the low density lipoprotien (LDL) of blood. The steps are-
   • Uptake of cholesterol into the less of the adrenal cortex.
   • Side chain cleavage of cholesterol by the mitochondrial enzyme 20,22 desmolase which converts cholesterol to pregnenolone , a common precursor of all steroid hormones.
   • Conversion of pregnenolone to 11-deoxycortisol and 11-deoxycorticosterone by hydroxylation reactions catalysed by enzymes 17 alpha hydroxylase, 3 beta dehydrogenase and 21 hydroxylase.
   • Conversion of 11-deoxycortisol to cortisol
   • Conversion of 11-deoxycorticosterone to corticosterone by the enzyme 11 beta hydroxylase
2. Mineralocorticoids - These incude aldosterone , deoxycorticosterone and 18 hydroxy-deoxycorticosterone. Aldosterone is secreted by the Zona Glomerulosa cells which constitute the outer one-fifth of the adrenal cortex. The steps are-
   • Uptake of cholesterol for the formation of corticosterone.
   • Formation of aldosterone by hydroxylation of some of the corticosterone and conversion to an aldehyde by aldosterone aynthase enzyme.
3. Catecholamines-  There are few steps by which these are synthhesized-
   • L-tyrosine is derived from diet or from the hepatic hydroxylation of L-phenylalanine by phenylalanine hydroxylase. L-tyrosine originates the biosynthetic pathway.
   • Conversion of Tyrosine to DOPA by enzyme tyrosine hydroxylase. This is the rate limiting step.
   • Conversion of DOPA to dopamine by enzyme dopa decarboxylase in the cortisol.
   • Conversion of Dopamine to Nor-Epinephrine by the enzyme dopamine beta-hydroxylase which requires molecular oxygen and ascorbate as hydrogen donor.
   • Conversion of norepinephrine to epinephrine in the cytoplasm by the enzyme Phenylethanolamine N-methyltransferase (PNMT) using S-adenosyl methionine as a methyl donor.
4. Adrenal sex steroids- These include dehydroepiandrosterone (DHEA) and androstenedione which are major androgenic precursor products of the adrenal cortex. These are synthesized in the Zona Reticularis part of the adrenal cortex. 
   • The starting point is 17-hydroxylated derivatives of pregnenolone and progesterone .
   • The 17-hydroxypregnenolone is converted to DHEA by the enzyme 17,20 desmolase.

Also Read: Body Fluid Compartments and its Measurement

Adrenal Hormones Metabolism

• Glucocorticoids are degraded in the liver and conjugated with glucuronic acid. There is enterohepatic circulation of glucocorticoids. About 70% of the conjugated steroids are excreted in the urine and 20% in the feces.
• Mineralocorticoids are mostly degraded in the liver and reduced to tetrahydroaldosterone, which is excreted in the urine.
• Androsterone and etiocholanolone are the end products of Sex hormones metabolism which are excreted in the urine.

Also Read: Membrane Potentials & Resting Membrane Potential

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