L4 Endocrine/diabetes Flashcards
What is each adrenal gland comprised of
- Two distinct structures, the outer part of the adrenal glands called the adrenal cortex
- The inner region is known as the adrenal medulla
Adrenal causes of hypertension
• Primary Hyperaldosteronism • Zona Glomerulosa ○ Adenoma ○ Hyperplasia ○ Rare genetic causes Phaeochromocytoma ( phaeo) • Tumour of the adrenal medulla • Some forms of Congenital Adrenal Hyperplasia • Enzyme defect - Uncommon
Layers of the adrenal gland
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
- Medulla
Adrenal causes of hypertension
- Primary hyperaldosteronism
- Zone glomerulosa
Adenoma
Hyperplasia
Rare genetic causes
Phaeochromocytoma - Tumour of the adrenal medulla
- Some forms of congenital adrenal hyperplasia
- Enzyme defect - uncommon
What is aldosterone produced by
- Zona glomerulosa of the adrenal cortex in the adrenal gland
Pathway for aldosterone secretion - RAAS
If the perfusion of the juxtaglomerular apparatus in the kidney’s macula densa decreases, then the juxtaglomerular cells (granular cells, modified pericytes in the glomerular capillary) release the enzyme renin.
Renin cleaves a decapeptide from angiotensinogen, a globular protein. The decapeptide is known as angiotensin I.
Angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme (ACE) which is thought to be found mainly in endothelial cells of the capillaries throughout the body, within the lungs and the epithelial cells of the kidneys.
Angiotensin II causes tcells to contract along with the blood vessels surrounding them and causing the release of aldosterone
What does activation of AT II receptors cause
- Vasodilation
- ADH secretion
What does activation of AT I receptors cause
- Vasoconstriction
- Sympathetic activation
Overall effects of renin, angiotensin and aldosterone
- Decrease K+ levels
- Increase Na+ levels
- Increase blood volume and pressure
What is primary hyperaldosteronism
Primary aldosteronism, also known as primary hyperaldosteronism or Conn’s syndrome, refers to the excess production of the hormone aldosterone from the adrenal glands, resulting in low renin levels.
Who do you screen for primary hyperaldosteronism
- Hypokalaemia
- Patients with resistant hypertension
- Younger people
Comparison of vascular and renal pathology between individuals with primary aldosteronism and essential hypertension and similar blood pressure
Individuals with PA have more vascular and renal pathology than people with essential hypertension and similar blood pressure
What do initial screening tests investigate for
- Suppressed renin
- Normal/high aldosterone
Confirmatory test for primary hyperaldosteronism
- Oral or IV Na+ suppression test
Primary hyperaldosteronism tests for specific aetiology ie secreting adenoma or bilateral hyperplasia
- Adrenal CT scan
- Adrenal venous sampling - Metomidate PET CT
What does primary hyperaldosteronism usually result from
- Aldosterone secreting adenoma of the adrenal cortex
Unilateral adenoma vs bilateral hyperplasia
Unilateral disease is usually caused by an aldosterone producing adenoma (benign tumor) and less commonly by adrenal cancer or hyperplasia (when the whole gland is hyperactive).
Bilateral disease is usually caused by bilateral hyperplasia (when both glands are hyperactive).
Treatment for unilateral adenoma
- Laparoscopic adrenalectomy
- Medical treatment (sometimes)
Treatment for bilateral hyperplasia
- Medical treatment (aldosterone antagonists)
- Spironolactone
What is a phaeochromocytoma
- Tumour of the adrenal medulla
how do sympathetic neurones in the spinal cord cause release of adrenalin and noradrenalin in the adrenal medulla
Symp neurones in spinal cord –Ach–> adrenal medulla
Tyrosine –> L-dopa –> dopamine –> noradrenalin –> adrenalin
Products of the adrenal medulla
· Catecholamines
- Dopamine
- Norepinephrine (noradrenalin) – cortisol–> epinephrine(adrenalin)
Is the adrenal medulla essential for life ‘stress/flight/fight’ response
Nope
Effects of noradrenalin (alpha 1 and 2)
- Vasoconstriction –> increased BP, pallor
- Glycogenolysis
Effects of adrenalin (alpha 1, beta 1 and 2)
- Vasoconstriction
- Vasodilatation in Muscle
- Increased heart rate
- Sweating
What percentage of phaeos are diagnosed in the mortuary
20%
How does a phaeochromocytoma present
· Spells
- Headache, sweating
- Pallor, palpitation
- Anxiety
· Hypertension
- Permanent
- Intermittent
Which genetic conditions are associated with phaeochromocytomas
· Neurofibromatosis Type 1 (NF1)
· Multiple endocrine neoplasia type 2 ( MEN 2 )
· Von hippel - lindau syndrome
When are tumors under the skin likely to appear
- May appear at any age but especially during adolescence
What are neurofibromas
- Tumors which grow on the nerves, are made up of cells that surround nerves and other cell types, are called neurofibromas
What is crowe’s sign
- The Crowe sign or Crowe’s sign is the presence of axillary (armpit) freckling in people with neurofibromatosis type I (von Recklinghausen’s disease). These freckles occur in up to 30% of people with the disease and their presence is one of six diagnostic criteria for neurofibromatosis.
What is von-hippel lindau syndrome
Is an inherited disorder characterized by the formation of tumors and fluid-filled sacs (cysts) in many different parts of the body
Which tumours are characteristic of von-hippel lindau syndrome
- Hemangioblastomas
What are hemangioblastomas
- These growths are made of newly formed blood vessels. Although they are typically noncancerous, they can cause serious or life-threatening complications.
- Hemangioblastomas that develop in the brain and spinal cord can cause headaches, vomiting, weakness, and a loss of muscle coordination (ataxia).
- Hemangioblastomas can also occur in the light-sensitive tissue that lines the back of the eye (the retina).
24 hour urine test for phaeochromocytomas
- Normetanephrines and metanephrines
- 3 Methoxytyromine
Plasma test for phaeochromocytomas
- Noradrenalin and adrenalin
- Metanephrines
What other things elevate the measured catecholamines
- Obstructive Sleep Apnoea
- Amphetamine like drugs
- L-DOPA
- Labetalol
What does urine dopamine come from
Kidney & Nervous system
NOT the Adrenal Medulla
So measure urine Methoxytyramine
What is an MIBG scan
An MIBG scan is a nuclear medicine scan that involves an injection of a radioactive medication (radiopharmaceutical) called iodine-123 meta-iodobenzylguanidine – MIBG for short
The radiopharmaceutical is injected into a vein usually on the inside of the elbow
Alpha blockers used to manage phaeochromocytomas
□ Phenoxybenzamine
□ Doxazocin
Beta blockers used to manage phaeochromocytomas
- Propanolol
What is laparoscopic adrenalectomy
Laparoscopic adrenalectomy is a minimally invasive technique used to remove a diseased or cancerous adrenal gland
Post adrenalectomy care
· Consider Genetic testing • 30% are genetic ( 13 mutations so far) · Annual Metanephrines • 24 hour urine • Plasma · Additional treatment if Malignant • 10%
