2. Endocrine Physiology The Adrenal Gland 1
Dr.Mouaadh abdelkarim
Assistant Professor of Physiology
Department of Physiology
2nd floor
Tel:

3. Adrenal (Suprarenal) Glands
Adrenal glands are paired,
pyramid-shaped organs at the
top of the kidneys.
Weigh 6-10 g.
Structurally and functionally, they are two glands in one
Adrenal cortex (80-90%)– glandular tissue derived from embryonic mesoderm
Adrenal medulla (10-20%)– formed from neural ectoderm, can be considered a modified sympathetic ganglion
Cortex
Medulla

4. Adrenal Cortex
Synthesizes and releases steroid hormones (corticosteroids)
Different corticosteroids are produced in each of the three layers:
Zona glomerulosa – mineralocorticoids (mainly aldosterone)
Zona fasciculata – glucocorticoids +Androgens (mainly cortisol and corticosterone)
Zona reticularis – gonadocorticoids + glucocorticoids (mainly dehydroepiandrosterone DHEA)

5. Adrenal Gland
Guyton and Hall

6. Adrenal Cortex
Salt
Sugar
Sex
Guyton and Hall

7. HPA Axis
Guyton and Hall

8. Steroid Hormones: Structure
Guyton and Hall

9. Steroid Hormones Synthesis
Steroids are derivatives of cholesterol
Cholesterol is from the lipid droplets
in cortical cells
Removed cholesterol is replenished by cholesterol in LDL in blood or synthesized from acetate

10. Steroid Hormones Synthesis (Cont.)
Steroid hormones are synthesized and secreted on demand (not stored)
The first and rate-limiting step in the synthesis of all steroid hormones is conversion of cholesterol to pregnenolone by the enzyme cholesterol dismolase (cholesterol side chain cleavage enzyme (SCC))
Newly synthesized steroid hormones are rapidly secreted from the cell
Following secretion, all steroids bind to some extent to plasma proteins: CBG (corticosteroid binding globulin) and albumin

11. Steroidogenesis: Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones

12. Genetic Defects in Adrenal Steroidogenesis
Congenital adrenal hyperplasias: Congenital adrenal hyperplasia (CAH) are any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands (steroidogenesis).
ACTH
ِAdrenal hyperplasia
cortisol

13. Congenital adrenal hyperplasias
21-hydroxylase (P450c21) deficiency:
cortisol, corticosterone, and aldosterone deficiency
*ACTH Adrenal hypertrophy and high amounts of androgen
* Virilization of female (masculanization)

14. Steroid Hormones: Action
Guyton and Hall

15. Hormones of adrenal cortex
production
mg/day
concentr.
ng/ml
activity
MINERAL.
GLUCO.
aldosterone
0.15
90%
deoxycorti-costerone
0.6
1/15
corticoste-rone
1-4
2-4
1/50 4%
cortisol
8-25
40-180
1/400
95%
DHEA
7-15 5
Koncentrace DHEA závisí na věku, maximum je kolem roku

16. 1- Cortisol is at 1000 fold higher concentrations than aldosterone 2- Corticosterone >>>>aldosterone 3- Cortisol binds well to the mineralocorticoid receptor

17. Mineralocorticoids: Aldosterone
A steroid hormone.
Essential for life.
Synthesized in zona glomerulosa
Responsible for regulating Na+ reabsorption in the distal tubule and the cortical collecting duct
Target cells are called “principal (P) cell”.
It also affects Na+ reabsorption by sweat, salivary and intestinal cells.
* Stimulates synthesis of more Na/K-ATPase pumps.

18. Mineralocorticoids: Aldosterone
Aldosterone secretion is stimulated by:
Decreasing blood volume or pressure (renin-angeotensin system).
Rising blood levels of K+
Low blood Na+
ACTH

19. Aldosterone synthesis
Voltage-sensitive calcium channels open and the intracellular calcium concentration increases—activating calcium calmodulin kinase.
Calcium channel blockers inhibit aldosterone synthesis.

20. Aldosterone levels fluctuate diurnally—highest concentration being at 8 AM, lowest at 11 PM, in parallel to cortisol rhythms.

22. The Four Mechanisms of Aldosterone Secretion
Renin-angiotensin mechanism – kidneys release renin, which stimulates angiotensin II that in turn stimulates aldosterone release
Plasma concentration of potassium and sodium– directly influences the zona glomerulosa cells
ACTH – causes small increases of aldosterone during stress
Atrial natriuretic peptide (ANP) – inhibits activity of the zona glomerulosa

23. The Four Mechanisms of Aldosterone Secretion
Guyton and Hall

24. Actions of Aldosterone
Stimulates sodium reabsorption by distal tubule and collecting duct of the nephron and promotes potassium and hydrogen ion excretion
Increases transcription of Na/K pump
Increases the expression of apical Na channels and an Na/K/Cl cotransporter
Expands ECF volume

25. Aldosterone binds to the mineralocorticoid receptor in target cells and affects transcriptional changes typical of steroid hormone action.
The kidney is the major site of mineralocorticoid activity.

26. Aldosterone: Role in diseases
Complete failure to secrete aldosterone leads to death (dehydration, low blood volume).
Hyperaldosterone states: Contribute to hypertension associated with increased blood volume.

27. Overproduction of aldosterone
primary causes, ie. Conn’s syndrome
adenoma, nodular hyperplasia of zona glomerulosa
secondary
cirrhosis, ascites, nephrotic syndrome
symptoms, signs
headache, hypokalemia causing muscle weakness, hypernatremia, hypervolemia, nocturnal polyuria, hand cramping

28. J winker

29. Overproduction of aldosterone
treatment
surgical for adenoma
Spironolactone

30. Thank you
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