Adrenal cortex and adrenal causes of hypertension Flashcards
What are the endocrine causes of HTN?
Adrenal
Acromegaly - excess of growth hormone
Thyroid dysfunction
What is primary hyperaldosteronism?
Rare condition causing aldosterone hyper-secretion from an adenoma or hyperplasia of the zona glomerulosa.
Why is there HTN and hypokalaemia in primary hyperaldosteronism?
Aldosterone helps control blood pressure by holding onto salt and losing potassium from the blood (RAAS). The increased salt increases the blood pressure. The more aldosterone, the more potassium lost.
Why does primary hyperaldosteronism increase the risk of cardiac events?
HTN
Aldosterone receptors in cardiac tissue and vascular smooth muscle as well.
When would primary hyperaldosteronism be suspected?
Severe HTN <40 years
Diuretic induced hypokalaemia
Adrenal incidentoloma
FHx of early onset HTN or haemorrhage CVA at young age
Metabolic alkalosis
What investigations can be done when suspecting hyperaldosteronism?
Renin aldosterone ratio
Dynamic testing - Saline suppression test
Adrenal CT
Molecular imaging - Metomidate PET CT
Adrenal venous sampling
What happens to renin and aldosterone levels in primary hyperaldosteronism?
How is a saline suppression test done?
Infuse saline or oral saline loading.
Measure plasma aldosterone. Unable to suppress = PHA.
Ensure K+ corrected before otherwise false results (Love K+ inhibits aldosterone production)
Stop interfering medications (Diuretics - 4 weeks, BBlockers, ACEI - 2 weeks)
How is hyperaldosteronism treated?
Medically - Aldosterone antagonists (spironolactone, Amiloride) to treat hypokalaemia and HTN.
Surgically - Curative to treat unilateral disease.
What is a phaeochromocytoma?
Tumour in the adrenal medulla that produces excess catecholamines due to increased production of chromatin cells.
What is the synthesis pathway of catecholamines?
Tyrosine –> L-dopa –> Dopamine –> Noradrenaline –> Adrenaline
Increased production of Noradrenaline can cause what biologically?
Vasoconstriction
Glycogenolysis
Increased production of Adrenaline can cause what biologically?
Vasoconstriction
Increased HR
Sweating
What are the clinical features of phaemochromocytoma?
Headache, sweating, palpitations
HTN, tachcardia
Chest or abdo pain
Pallor/flush
Sense of impending doom
Episodic
Precipitating factors e.g. position change, anxiety, medications
Phaeochromocytoma has genetic associations to which syndromes?
MEN 2 (Multiple Endocrine Neoplasia) - from RET photo-oncogene
VHL (Von Hippel-Lindau) - VHL gene
NF1 (Neurofibromatosis Type 1) - NF1 gene
PGL 1 (Paraganglioma) - SDHD (Succinate dehydrogenase complex subunit D)
PGL 4 - SDHB (Subunit B)
When would genetic testing be carried out with someone with phaeochromocytoma?
Aged <20 at diagnosis
FHx of phaeochromocytos or paragangliomas
Features of syndrome
Bilateral adrenal phaeochromocytoma
Paraganglioma
What is the best imaging to do when suspecting someone with a phaeochromocytoma?
MIBG scan - a nuclear medicine scan that detects noradrenaline secreting tumours.
What biochemistry tests can be done when suspecting phaeochromocytoma?
Plasma free metanephrines
24 hour urine catecholamine
24 hours urine metanephrines
What are the typical features of a phaeochromocytoma on a CT scan?
> 3cm in size
Irregular/heterogenous appearance due to bleeding and calcification.
Hounsfield units >20 as little fat.
How is phaeochromocytoma treated?
Alpha blockade - Doxazocin, Penoxybenzamine
Beta Blockade - Propanolol
Surgery - Laparoscopic adrenalectomy
Which genetic association of phaeochromocytoma has increased malignant potential?
SDHB gene - causes PGL 4
What is the ‘rule of 10’ for phaeochromocytomas?
10% are bilateral
10% metastatic
10% extra-adrenal
What are adrenal incidentalomas?
Unsuspected tumours on the adrenal glands, found incidentally.
What are adrenal incidentalomas most likely to be?
Non-secreting lesions (75%)
10% phaeochromocytomas
10% malignancy
When assessing an adrenal incidentaloma, what are the three tests done?
ONDST
Metanephrines
Renin:Aldosterone ratio
These check for the causes of adrenal hypertension
For a benign adrenal nodule, what is the hounsfield unit likely to be?
<10 HU as there is more fat.
What is congenital adrenal hyperplasia?
A metabolic disorder related to enzymatic defects in the biosynthesis of cortical steroids.
Autosomal recessive
What happens to the hormones in congenital adrenal hyperplasia?
Low cortisol and/or aldosterone
Excess percursor steroids
Increased ACTH from pituitary as not enough cortisol to feedback.
Which gene deficiency causes 95% of cases of congenital adrenal hyperplasia?
21 hydroxylase
21 hyroxylase is located on which chromosome?
6p21 within the HLA histocompatibility complex
What are the two types of 21 hydroxylase deficiency?
Classic - more severe. Children. Salt losing (aldosterone deficient) or non-salt losing.
Non-classic - mild or late onset.
Why are metanephrines tested when suspecting phaeochromocytomas?
Metanephrines are a breakdown product of catecholamines. More metanephrines = more catecholamines.
Excess catecholamines = phaeochromocytoma
