1. Endocrine Revision

2. Learning objectives
• HPA axis
• Anatomy and physiology of thyroid gland
• Anatomy and physiology of adrenal glands
• Anatomy and physiology of pancreas
• Thyroid disorders
• Adrenal disorders
• Diabetes

3. Endocrine Physiology
• Regulation of hormonal release into the
bloodstream and control in the body.
– negative feedback mechanisms
• Negative feedback is seen when the output of a
pathway inhibits inputs to the pathway. Secretion
of anterior pituitary AND hypothalamic hormones
may be inhibited by the circulating hormones
whose release they stimulate, which is the basis
of negative feedback.

4. HYPOTHALAMUS

5. Hypothalamus

8. PITUITARY GLAND

9. Pituitary gland
(Hypophysis)
• Small ovoid organ
• Hangs from HYPOTHALAMUS by its INFUNDIBULAR
STALK
• Located in the Sella Turcica of the SPHENOID bone
{BASE OF CRANIUM}
• Enclosed by a CT Capsule
• Comprises 2 main parts:
anterior pituitary (adenohypophysis)
posterior pituitary (neurohypophysis)

10. Pituitary gland

11. HPA Axis

12. Pituitary gland

18. Acromegaly

19. Acromegaly – systemic effects

20. Acromegaly – investigations

21. Acromegaly – management

22. THYROID GLAND

23. Thyroid
• Bilobed; occurs in front of UPPER TRACHEA
• Develops from down-growth of FOETAL TONGUE
• PARATHYROIDS sit posteriorly (2 on each side)
• GOITRE – swelling of neck (enlargement of thyroid)

24. Thyroid

26. Thyroid hormone

28. Thyroid hormone

29. Thyroxine (T4) for hypothyroidism
• Side Effects = symptoms of hyperthyroidism
- tremor, restlessness, palpitations, diarrhoea,
vomiting, insomnia, weight-loss, heat intolerance…

30. ADRENAL GLANDS

31. Adrenal Glands
(Suprarenal glands)
• Situated above KIDNEYS
• Surrounded by a CT Capsule
• Divided into 2 main regions:
CORTEX (outer) 3 classes of steroid hormone,
mineralocorticoids, glucocorticoids, androgens
MEDULLA (inner) Catecholamine hormones,
adrenaline, noradrenaline

32. Adrenal gland
Pregnenolone is an
endogenous steroid
hormone involved in the
steroidogenesis of
progestogens,
mineralocorticoids,
glucocorticoids,
androgens and
oestrogens
McGeown Physiology

33. Adrenal cortex
• Adrenal steroids are lipophilic. They cross the plasma membrane of target cells and bind to
intracellular receptors, then the receptor-hormone complex enters the nucleus.

34. Adrenal cortex has 3 zones:
ZONA GLOMERULOSA (outermost)
rounded groups of cells
- MINERALOCORTICOIDS
ZONA FASCICULATA (middle)
large vacuolated cells in columns –
under control of ACTH from
anterior pituitary
- GLUCOCORTICOIDS
ZONA RETICULARIS (innermost)
cells arranged in branching,
irregular networks
- ANDROGENS

35. Mineralocorticoids
Aldosterone is regulated by:
• Renin-angiotensin-aldosterone-system – activated by
reduction in ECF, arterial BP or plasma [sodium] (kidney
detects this). This causes increase in angiotensin II, which
stimulates aldosterone secretion. Maintains blood pressure.
• Increases in potassium
• Adrenocorticotrophic hormone (ACTH) from anterior pituitary
Actions of Aldosterone:
• Reabsorption of Na+ – from distal convoluted tubule. Expands
ECF and plasma volumes.
• Secretion of K+ – active secretion into the distal convoluted
tubule, without parallel movement of water
• Secretion of H+ – into the distal convoluted tubule

36. Adrenal androgens
• Stimulated by ACTH.
• Main source of androgens in the female.
• Adrenal Medulla
• An endocrine extension of the sympathetic
NS, containing chromaffin cells.
• Releases catecholamines: noradrenaline and
adrenaline.

37. • METABOLIC ACTIONS
• Activation of the adrenal medulla, either in response to
stress or hypoglycaemia, will act to increase the blood
sugar.
• ↑ metabolism and heat production
• ↑glycogenolysis
• ↑ gluconeogenesis
• ↓ glucose uptake
• ↑ fat breakdown
• -with ↑ fatty acid oxidation and ketone production
Adrenal androgens

38. Mineralocorticoids –regulation of aldosterone secretion
stimuli
RAAS

39. Glucocorticoids
Have a major role in control of blood glucose, and in
body’s response to stress.
Cortisol is mainly regulated by:
• Plasma level of ACTH under stimulation during times
of stress (trauma, anxiety, infection)
• fluctuates during the normal circadian rhythm (peak
in the morning)

40. Mechanism of action and effects
of corticosteroids

42. C Central obesity
Cervical fat pads
Comedones
U Urinary free glucose and cortisol increased
S Striae
Supressed immunity
H Hypercortisolism
Hypertension
Hirsutism
Hyperglycaemia
I Iatrogenic (increased administration of corticosteroids)
N Neoplasms
G Glucose intolerance
Growth retardation

43. Hypoadrenalism – Addison’s disease
• Primary - failure of adrenal cortex which
decreases the negative feedback, and
increases the amount of ACTH.
• Secondary – failure of the gland to be
stimulated by ACTH.

44. Hypoadrenalism – Addison’s disease

46. Adrenal medulla

47. PANCREAS

49. Pancreas
• Islets of LANGERHANS – endocrine portion
• Islets possess 4 types of endocrine cell:

50. Carbohydrate Metabolism
-Stimulates glucose uptake (except in brain)
-Promotes glycogen storage
-Stimulates glucose use for energy (stimulates glycogenolysis)
Protein Metabolism
Promotes protein accumulation within cells by:
-stimulating amino acid uptake -stimulating synthesis and inhibiting
breakdown
Lipid Metabolism
Promotes triglyceride deposition by:
-inhibiting breakdown of hormone-sensitive lipase
-stimulating fatty acid synthesis
-promoting fatty acid release
Insulin