Suprarenal Glands

• Divided into two parts; each with separate functions

• Suprarenal Cortex

• Suprarenal Medulla

ADRENAL GLAND HORMONES

The Adrenal Gland

The adrenal systemvitally important for

the survival of stress

Preparation for

flight or fight

The Adrenal Glands

• Adrenal medulla

• Adrenal cortex

Three specific zones and each produces a specific class of steroid hormone

Zona glomerulosa –mineralocorticoids (Aldosterone)

Zona fasciculata –glucocorticoids ( Cortisole )

Zona reticularis -androgens

Steroid biosynthesis: 3 main pathways

“corticoid” = ..from the cortex

“minerals” = Na+, K+,..

“gluco..” = increases sugar “andros” = male

“gen..”= generate

Mineralocorticoid

Pathway

Glucocorticoid

Pathway

Androgen Pathway

Steroid biosynthesis:

The 3 main pathways.

Biosynthetic pathway

of Adrenal cortex

hormones:

Mineralocorticoids

• Aldosterone exerts the 90% of the mineralocorticoid activity. Cortisol also have mineralocorticoid activity, but

only 1/400th that of aldosterone.

• Aldosterone increases renal tubular (principal cells) reabsorption of sodium & secretion of potassium

• Aldosterone stimulates sodium & potassium transport in sweat glands, salivary glands, & intestinal epithelial cells

Action

s of

aldost

erone

Regulation of

aldosterone secretion

Renin-Angiotension-Aldosterone System Mode of Action of Aldosterone

Associated Clinical Conditions

Hyperaldosteronism:

The overproduction of aldosterone by the adrenal glands

Leads to arterial hypertension (high blood pressure) associated with hypokalemia, usually a

diagnostic clue.

Conn’s syndrome is primary hyperaldosteronism caused by an aldosterone-producing adenoma.

Hypoaldosteronism:

This condition may result in hyperkalemia.

It can also cause urinary sodium wasting, leading to volume depletion and hypotension.

Hormones of the Adrenal Cortex

(Glucocorticoids)

Glucocorticoids (including cortisone and cortisol)

Produced in the middle layer of the adrenal cortex

Promote normal cell metabolism

Help resist long-term stressors

Released in response to increased blood levels of ACTH

Effect of cortisol on protein metabolism

• Reduction of protein storage in all cells

except those of liver – ↑ protein

catabolism & ↓ protein synthesis

• Cortisol increases liver & plasma proteins

• Mobilizes aminoacids from non hepatic

cells, thus increase blood amino acid

level.

• ↑ amino acid transport to liver cells & ↓

transport of amino acids into other cells

Functions of glucocorticoids REGULATION OF CORTISOL SECRETION

Hormones of the Adrenal Cortex

Sex hormones

Produced in the inner layer of the adrenal cortex

Androgens (male) and some estrogen (female)

stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors.

Androgens

Different class of Androgens

Dihydroepiandrosterone

(DHEA)

Androstenediol

Androstenedione

Dyhydrotestosterone

Functions of Androgen Hormones

Testes formation

Androgens regulates certain Y chromosome genes, particularly

SRY, control development of the male phenotype, including

conversion of the early bipotential gonad into testes.

Androgen effects:

Acts as paracrine hormone required by the Sertoli cells in order to

support sperm production

During puberty, they stimulate the germ cells to differentiate into

sperm.

Spermatogenesis

Inhibition of fat deposition

Increase muscle mass

Hormones of the Adrenal Medulla

Produces two similar hormones (catecholamines)

Epinephrine

Norepinephrine

These hormones prepare the body to deal with short-term stress

Biosynthesis of catecholamines

A catecholamine (CA) is has a

catechol (benzene with two hydroxyl

side groups) and a side-chain amine.

They have a half-life of a few minutes when

circulating in the blood. They can be degraded

either by methylation by catechol-O-

methyltransferases (COMT) or by deamination by

monoamine oxidases (MAO).

Features of Catecholamines

Two catecholamines, norepinephrine and

dopamine, act as neuromodulator in the CNS and

as hormones in the blood circulation.

High catecholamine levels in blood are associated

with stress, which can be induced from

psychological reactions or environmental

stressors such as elevated sound levels,

intense light, or low blood sugar level.

Effects of Catecholamine

Catecholamines cause general physiological changes that prepare the body for physical activity

(fight-or-flight).

Some typical effects are increases in heart rate, blood pressure, blood glucose levels, and a

general reaction of the sympathetic nervous system.

Action of Epinephrine on a Liver Cell

1. Epinephrine is lipophobic and needs to bind to

specific receptor proteins on cell surface.

2. Acting through intermediary G proteins the hormone

bound receptor activates the enzyme adenenylyl cyclase

which converts ATP to cAMP

3. Cyclic AMP performs as a 2ndary messenger and

activates protein kinase-A an enzyme that was previously

inactive

4. Protein kinase–A phosphorylates and activates the

enzyme phosphorylase which catalyses the hydrolysis of

glycogen into glucose.

IP3/CA++ Second-Messenger System

1. The hormone epinephrine binds to specific receptor proteins

on the cell surface.

2. Acting through G- proteins, the hormone-bound receptor

activates the enzyme phospholipase C, which converts

membrane phospholipids into inositol triphosphate (IP3)

3. IP3 diffuses through the cytoplasm and binds to receptors on

the endoplasmic reticulum

4. The binding of IP3 to the receptor stimulates the endoplasmic

reticulum to release Ca++ into the cytoplasm

5. Some of the released Ca++ binds to the receptor protein

called calmodulin

6. The Ca++/Calmodulin complex activates other intracellular

proteins – producing the horomone effects

Disorders of the Adrenal Gland

1. Hypoaldosteronism

loss of water/Na+

Addison’s disease – low aldosterone & cortisol

2. Hyperaldosteronism

3. Cushing’s syndrome

Hyper secretion of cortisol, androgens, aldosterone

Cushing’s syndrome

Cushing's syndrome associated with prolonged

exposure to inappropriately high levels of the

hormone cortisol. This can be caused by taking

glucocorticoid drugs, or diseases that result in

excess cortisol, ACTH, or CRH levels.

Cause:

Most common cause of Cushing's syndrome is

exogenous administration of glucocorticoids

prescribed by a health care practitioner to treat

other diseases.

Effect of steroid treatment of a variety of

disorders such as asthma and rheumatoid

arthritis, or in immunosuppression after an organ

transplant.

Signs and symptoms

Rapid weight gain, particularly of the trunk and

face with sparing of the limbs (central obesity).

Growth of fat pads along the collar bone and on

the back of the neck (buffalo hump) and a round

face often referred to as a “moon face.”

Thinning of the skin (which causes easy

bruising and dryness, particularly the hands)

Hyperhydrosis (excess sweating),

Telangiectasia (dilation of capillaries),