Adrenal cortex and adrenal causes of hypertension

Question 1

What are the endocrine causes of HTN?

Answer 1

Adrenal
Acromegaly - excess of growth hormone
Thyroid dysfunction

Question 2

What is primary hyperaldosteronism?

Answer 2

Rare condition causing aldosterone hyper-secretion from an adenoma or hyperplasia of the zona glomerulosa.

Question 3

Why is there HTN and hypokalaemia in primary hyperaldosteronism?

Answer 3

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.

Question 4

Why does primary hyperaldosteronism increase the risk of cardiac events?

Answer 4

HTN
Aldosterone receptors in cardiac tissue and vascular smooth muscle as well.

Question 5

When would primary hyperaldosteronism be suspected?

Answer 5

Severe HTN <40 years
Diuretic induced hypokalaemia
Adrenal incidentoloma
FHx of early onset HTN or haemorrhage CVA at young age
Metabolic alkalosis

Question 6

What investigations can be done when suspecting hyperaldosteronism?

Answer 6

Renin aldosterone ratio
Dynamic testing - Saline suppression test
Adrenal CT
Molecular imaging - Metomidate PET CT
Adrenal venous sampling

Question 7

What happens to renin and aldosterone levels in primary hyperaldosteronism?

Answer 7

Question 8

How is a saline suppression test done?

Answer 8

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)

Question 9

How is hyperaldosteronism treated?

Answer 9

Medically - Aldosterone antagonists (spironolactone, Amiloride) to treat hypokalaemia and HTN.
Surgically - Curative to treat unilateral disease.

Question 10

What is a phaeochromocytoma?

Answer 10

Tumour in the adrenal medulla that produces excess catecholamines due to increased production of chromatin cells.

Question 11

What is the synthesis pathway of catecholamines?

Answer 11

Tyrosine –> L-dopa –> Dopamine –> Noradrenaline –> Adrenaline

Question 12

Increased production of Noradrenaline can cause what biologically?

Answer 12

Vasoconstriction
Glycogenolysis

Question 13

Increased production of Adrenaline can cause what biologically?

Answer 13

Vasoconstriction
Increased HR
Sweating

Question 14

What are the clinical features of phaemochromocytoma?

Answer 14

Headache, sweating, palpitations
HTN, tachcardia
Chest or abdo pain
Pallor/flush
Sense of impending doom
Episodic
Precipitating factors e.g. position change, anxiety, medications

Question 15

Phaeochromocytoma has genetic associations to which syndromes?

Answer 15

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)

Question 16

When would genetic testing be carried out with someone with phaeochromocytoma?

Answer 16

Aged <20 at diagnosis
FHx of phaeochromocytos or paragangliomas
Features of syndrome
Bilateral adrenal phaeochromocytoma
Paraganglioma

Question 17

What is the best imaging to do when suspecting someone with a phaeochromocytoma?

Answer 17

MIBG scan - a nuclear medicine scan that detects noradrenaline secreting tumours.

Question 18

What biochemistry tests can be done when suspecting phaeochromocytoma?

Answer 18

Plasma free metanephrines
24 hour urine catecholamine
24 hours urine metanephrines

Question 19

What are the typical features of a phaeochromocytoma on a CT scan?

Answer 19

> 3cm in size
Irregular/heterogenous appearance due to bleeding and calcification.
Hounsfield units >20 as little fat.

Question 20

How is phaeochromocytoma treated?

Answer 20

Alpha blockade - Doxazocin, Penoxybenzamine
Beta Blockade - Propanolol
Surgery - Laparoscopic adrenalectomy

Question 21

Which genetic association of phaeochromocytoma has increased malignant potential?

Answer 21

SDHB gene - causes PGL 4

Question 22

What is the ‘rule of 10’ for phaeochromocytomas?

Answer 22

10% are bilateral
10% metastatic
10% extra-adrenal

Question 23

What are adrenal incidentalomas?

Answer 23

Unsuspected tumours on the adrenal glands, found incidentally.

Question 24

What are adrenal incidentalomas most likely to be?

Answer 24

Non-secreting lesions (75%)
10% phaeochromocytomas
10% malignancy

Question 25

When assessing an adrenal incidentaloma, what are the three tests done?

Answer 25

ONDST
Metanephrines
Renin:Aldosterone ratio
These check for the causes of adrenal hypertension

Question 26

For a benign adrenal nodule, what is the hounsfield unit likely to be?

Answer 26

<10 HU as there is more fat.

Question 27

What is congenital adrenal hyperplasia?

Answer 27

A metabolic disorder related to enzymatic defects in the biosynthesis of cortical steroids.
Autosomal recessive

Question 28

What happens to the hormones in congenital adrenal hyperplasia?

Answer 28

Low cortisol and/or aldosterone
Excess percursor steroids
Increased ACTH from pituitary as not enough cortisol to feedback.

Question 29

Which gene deficiency causes 95% of cases of congenital adrenal hyperplasia?

Answer 29

21 hydroxylase

Question 30

21 hyroxylase is located on which chromosome?

Answer 30

6p21 within the HLA histocompatibility complex

Question 31

What are the two types of 21 hydroxylase deficiency?

Answer 31

Classic - more severe. Children. Salt losing (aldosterone deficient) or non-salt losing.
Non-classic - mild or late onset.

Question 32

Why are metanephrines tested when suspecting phaeochromocytomas?

Answer 32

Metanephrines are a breakdown product of catecholamines. More metanephrines = more catecholamines.
Excess catecholamines = phaeochromocytoma