Adrenal Cortex

1
Adrenal hormones

• M.Prasad Naidu
• MSc Medical Biochemistry,
• Ph.D.Research Scholar

2
Functional anatomy

• 2 adrenal glands / suprarenal glands
• Situated on the upper pole of each kidney
• Each gland weighs 4 gms
• 2 distinct parts (Cortex medulla )
• A.medulla is the central portion (20)
• A. cortex is the outer portion (80)
• The 2 portions developmentally,functionlly
  structurally diff from each other.

3
Functional anatomy

• A. medulla develops from the neural crest, which
  gives origin to sympathetic nervous system.
• So its secretions resemble that of sympathetic
  nervous system.
• A.cortex develops from mesonephros, which give
  rise to the renal tissues.
• It secretes a group of hormones called
  Corticosteroids

4
Histology of A. cortex

• 3 distinct layers.
• 1.Zona glomerulosa- outer most layer-secretes
  mineralocorticoids
• 2.Zona fasciculata- middle layer secretes
  mostly GCs and to slight extent sex hormones.
• 3.Zona reticularis- inner most layer mostly
  sex hormones slightly GCs.

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Hormones of A.Cortex

• Adrenocortical hormones / corticosteroids
• Synthesized from cholesterol
• Degraded mainly in the liver and conjugated to
  form glucuronides and to a lesser extent of
  sulphates.
• 25 excreted in bile feces 75 in the urine
• 1. Mineralocorticoids
• 2. Glucocorticoids
• 3. Sex hormones

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mineralocorticoids

• Act on the metabolism of the electrolytes or
  minerals distribution of water in tissues.
• Especially Na K hence the name
• Eg Aldosterone (0.15µg of daily output)
• (0.006µg of plasma level)
• 11-Deoxycorticosterone(0.2µg) (0.006)
• Synthesis- CHOLESTEROL
• Transport- Aldosterone binds with plasma
  proteins (Gbs) binding is loose 50 of
  Aldosterone is found free.

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chemistry

• C21 steroids
• 90 MC activity is by aldosterone.
• Aldosterone is 30 times more active than
  deoxycorticosterone.
• Aldosterone is mainly concerned with water salt
  balance of the body.

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Functions of MCs

• Ald is essential for life (life saving hormone
• Total loss of Corticosteroids causes death within
  3 days to 2 weeks
• This is mainly bcos of MCs.
• Without MCs, the K conc of ECF rises
• The conc of Na Cl ions decreases
• The total ECF volume and Blood vol are also
  greatly reduced.
• All these changes lead to cardiac dysfunction,
  shock like state and finally death.
• The entire sequence can be prevented by Ald.
• Hence it is called life saving hormone.

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Functions of MCs

• 2 most important functions of aldosterone
• ?reabsorption of Na excretion of K in the
  renal tubules.
• ? secretion of H into the tubules to some extent

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Other functions

• Effect on Na reabsorption -
• Ald acts on the DCT and the collecting duct and
  increases the reabsorption of Na
• Effect on ECF volume B.P- The MCs cause
  persistent increase in ECF fluid vol and the
  blood vol. This finally leads to ?bp
• Effect on K ions- ? K excretion through the
  renal tubules.

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Other functions

• Effect on H-when ald ? Na reabs in the renal
  tubules, it causes tubular secretion of H. To
  some extent it is in exchange for Na ions.
• In normal conditions, ald is essential to
  maintain acid-balance in the body.
• In hypersecretion, it causes alkalosis
• In hyposecretion, it causes acidosis

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Other functions

• Effects on sweat glands salivary glands
• Ald has almost similar effect on sweat salivary
  glands as it has on the renal tubules.
• Na is reabsorbed from sweat glands under the
  influence of aldosterone, thus the loss of Na
  from the body is prevented.
• Effect on Intestine- loss of ald leads to loss
  of Na and water through the large intestine
  leading to diarrhea with loss of salt from the
  body.

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Mode of axn

• Ald acts through the m-RNA mechanism
• The sequence of events are
• i)As ald is sol in lipid, it diffuses readily
  into the interior of the tubular epithelial cells
  via the lipid layer of the cell membrane
• ii) in the cytoplasm of the tub.epi.cells, ald
  combines with the specific receptor protein

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Mode of axn

• iii) the ald.rec.complex diffuses into the
  nucleus
• iv) the m-RNA diffuses back into the cytoplasm.
  In the cytoplasm along with ribosomes causes
  protein syn.
• One of such enzymes that helps in the tpt of Na
  K through NaK pump is the NaK
  adenosinetriphosphatase

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Regulation of secretion

• Stimulating agents-
• 1. ? in the K conc in the ECF
• 2. ? in the Na conc in the ECF
• 3. ? in the ECF volume
• 4. ACTH