Endocrine Revision

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

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.

HYPOTHALAMUS

Hypothalamus

PITUITARY GLAND

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)

Pituitary gland

HPA Axis

Pituitary gland

Acromegaly

Acromegaly – systemic effects

Acromegaly – investigations

Acromegaly – management

THYROID GLAND

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)

Thyroid

Thyroid hormone

http://www.google.co.uk/url?sa=i&rct=j&q=hyperthyroidism&source=images&cd=&cad=rja&docid=Dwpm1dOXOomBwM&tbnid=RqVquDev5XD_wM:&ved=0CAUQjRw&url=http://cncplan.blogspot.com/2010/04/what-is-hyperthyroidism-graves-disease.html&ei=4ZRyUbWyHs6Z0AWFn4HgCA&bvm=bv.45512109,d.d2k&psig=AFQjCNEiv66Tr8qRhCXOaOhRMubI45TZyQ&ust=1366550108001593

Thyroid hormone

Thyroxine (T4) for hypothyroidism

• Side Effects = symptoms of hyperthyroidism

- tremor, restlessness, palpitations, diarrhoea, vomiting, insomnia, weight-loss, heat intolerance…

ADRENAL GLANDS

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

Adrenal gland

Pregnenolone is an endogenous steroid hormone involved in the steroidogenesis of progestogens, mineralocorticoids, glucocorticoids, androgens and oestrogens

McGeown Physiology

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.

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

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

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.

• 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

Mineralocorticoids – regulation of aldosterone secretion

stimuli

RAAS

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)

Mechanism of action and effects of corticosteroids

http://www.google.co.uk/url?sa=i&rct=j&q=side+effects+of+corticosteroids&source=images&cd=&cad=rja&docid=O9IV4zjyVvFBMM&tbnid=FOlmfgNV8I6ATM:&ved=0CAUQjRw&url=https://www.healthtap.com/topics/afrin-nose-spray-side-effects&ei=JYNyUePODuXU0QXvkYGYBg&bvm=bv.45512109,d.d2k&psig=AFQjCNFS5eZLQKe1FeGXW8VKdOXowfql4g&ust=1366545565766014

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

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.

Hypoadrenalism – Addison’s disease

http://www.google.co.uk/url?sa=i&rct=j&q=addisons+disease&source=images&cd=&cad=rja&docid=CdDegAOGQ5-WSM&tbnid=NEPQJOavwefCLM:&ved=0CAUQjRw&url=http://www.cidpusa.org/addison_disease_pictures.htm&ei=3vhyUdvUJMT60gXP_oDQCg&bvm=bv.45512109,d.d2k&psig=AFQjCNGqnkwLF4qXxDtl8IdCoGQoI7GPEw&ust=1366575625286555

Adrenal medulla

PANCREAS

http://www.google.co.uk/url?sa=i&rct=j&q=endocrine+pancreas&source=images&cd=&cad=rja&docid=i59l_j1ryO0a5M&tbnid=aLKpWLlCVHIt2M:&ved=0CAUQjRw&url=http://imageradiology.blogspot.com/2012/04/pancreas-anatomy-and-functions.html&ei=GX9yUdTzLu6V0QW484Ag&bvm=bv.45512109,d.d2k&psig=AFQjCNEVFFyHWZG7Lw2GNN2c5iWyhpYqXA&ust=1366544315813443

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

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

http://www.studyblue.com/notes/note/n/ch-47-chemical-signals-in-animals/deck/3085387