Adrenal gland lab diagnostics Flashcards
Laboratory data of a patient with arterial hypertension include increased Na+ and decreased K+ concentrations. Urinary aldosterone excretion is twice normal. What is the most likely diagnosis if plasma renin activity is A) high, B) low?
If renin is high:
- Secondary hyperaldosteronism (Renin secreting tumor - renin increase production of aldosterone). Another secondary reason could be Renal artery stenosis (reduced blood supply induce renin secretion).
If renin is low:
- Primary hyperaldosteronism (overproduction of aldosterone in the adrenal gland).
Mainly due to adrenal adenoma (Conn’s disease - 66%), and Bilateral idiopathic hyperplasia (30%).
Plasma cortisol level of a patient is lower than normal. Urinary aldosterone excretion is decreased and the patient is hypoglycemic.
What is the most likely diagnosis and what tests would you order?
Conclusion:
Since both the hormones produced in the adrenal gland are decreased, we should suspect primary hypoadrenalism like Addison’s disease or lack of ACTH production.Waterson-Friedchson syndrome (meningoccoal sepsis) can cause an adrenal shock state which presents like Addison’s disease. W-F is life threatening, Addison’s needs treatment but is not life threatening.
Tests:
- Check the serum ACTH, sodium, and potassium (suspected high).
- ACTH stimulation test to see if there is a cortisol increase in the serum (expect fail in Addison’s).
A 24-year-old man complains of gradually increasing weakness, weight loss and loss of appetite. He was observed to have bronzed skin, however, he reported no exposure to the sun. He was hypotensive and showed evidence of muscle wasting.
The results of the laboratory test included: serum Na+ 125 mmol/l, serum K+ 6.2 mmol/l, plasma cortisol: 4 μg/dl (8:00 a.m.) (decreased), plasma ACTH: increased above normal. An ACTH stimulation test failed to elicit response in plasma cortisol level.
What is the most likely diagnosis?
Serum sodium: 134 - 145 mM
Serum potassium: 3.5 - 5 mM
Plasma cortisol: 5 - 25 μg/dL
Conclusion: Due to a suspected decrease in both cortisol and aldosterone, with increased potassium / decreased sodium and increased ACTH, Addison’s disease is strongly indicated.
Further tests: Also check for a possible meningoccocal infection (W-F syndroem)
A patient with Cushing’s syndrome entered the hospital for diagnostic studies. Baseline plasma cortisol was elevated. A small dose of dexamethasone did not suppress cortisol but 50% reduction occurred when large dose of dexamethasone was given. Plasma ACTH was elevated. What is the most likely diagnosis?
Conclusion: Dexamethasone supression test: low dose did not supress (which implies Cushing’s syndrome) but a high dose supressed cortisol by 50%, with an ACTH increase. This is indicative that the problem lies in the pituitary gland → Cushing’s disease (pituitary adenoma).
Further tests: Imaging tests to determine adenoma presence
A hypertensive male patient enters the hospital for medical evaluation. His blood pressure is 180/95 mmHg; Serum Na+: 148 mmol/l, K+: 3.5 mmol/l, fasting plasma glucose: 7.2 mmol/l. Baseline plasma cortisol was elevated. A small dose of dexamethasone did not suppress cortisol. A large dose of dexamethasone was given but there was little change in the blood cortisol from baseline values. Plasma ACTH was high. What is the most likely diagnosis?
Serum sodium: 134 - 145 mM
Serum potassium: 3.5 - 5 mM
Serum fasting glucose: 3 - 6 mM
Plasma cortisol: 5 - 25 μg/dL
Conclusion: Dexamethasone supression test: neither low nor high dose supressed the cortisol level (Cushing’s syndrome indicated), and the serum level of ACTH is high. This incidates that there is an ectopic ACTH syndrome (secretion of ACTH elsewhere than the pituitary).
Together there is a clear indication for Cushing’s syndrome with ectopic ACTH production (e.g. small cell lung cancer).
Adrenal diabetes: blood glucose in the diabetic range due to excess cortisol (cortisol stimulates gluconeogenesis and desensitizes insulin).
A 40-year-old woman complains of amenorrhea and emotional disturbances, perhaps partially due to her increasing obesity which is concentrated around the chest and the abdomen. Her X-ray studies show evidence of mineral bone loss (osteoporosis). Laboratory results: serum K+ 3.2 mmol/l, fasting plasma glucose: 7.7 mmol/l, plasma cortisol: 40 μg/dl (8:00 a.m.) (elevated), plasma ACTH is lower than normal. A large dose of dexamethasone did not suppress the elevated cortisol level.
What is the most likely diagnosis?
Dexamethasone suppression test: Either low or high dose suppressed the cortisol level, and the ACTH levels are low. This indicate an ACTH-independent type of Cushing’s syndrome usually caused by an adrenal tumor (Conn’s disease).
A young girl develops virilization and hypertension. Plasma cortisol is low, ACTH is elevated.
What is the most likely cause of this condition? How are adrenal production of glucocorticoids, mineralocorticoids and androgens affected?
this indicates androgenital syndrome (lack of 11β-hydroxylase enzyme). This enzyme lack will lead to accumulation of the mineralocorticoid 11-dehydroxycorticosterone. This induces sodium and water retension, which causes the hypertension. It will also push synthetic pathways towards androgen production (virilization).
A young boy develops precocious puberty and arterial hypotension. Plasma ACTH is elevated, serum Na+ is low.
The deficiency of which enzyme is presumably responsible for the the above findings? Urinary excretion of 17-ketosteroids, DHEA and free cortisol are probably normal, low or elevated?
The deficient enzyme here is 21-hydroxylase, which catalyzes the conversion of prenonelone to 11-DOC. The accumulation of pregnonelone (no mineralocorticoid effect) will cause sodium and water depletion leading to hypotension. It also pushes synthetic pathways towards androgen synthesis, which leads to an accumulation of 17-ketosteroids and DHAP (dihydroepiandrosterone), which can usually be found in urine and plasma. Plasma cortisol is depleted because there is a deficiency in the cortisol metabolic pathway.
A 40-year-old man complains of spells of headache, profuse perspiration (diaphoresis), nausea and palpitations. Arterial blood pressure is markedly elevated. Urinary VMA excretion is increased.
What is the most likely diagnosis? What test would you order to confirm your diagnosis?
This is most likely due to a tumor in the adrenal medulla - phenochromocytoma.
Further tests:
- Glucagone stimulation test.Larger than 3-fold increases in plasma norepinephrine after glucagon strongly predicted the presence of a pheochromocytoma
- Clonidine suppression test. [Clonidine acts via the alpha pre-ganglionic receptors to reduce catecholamine secretion.
In normals, even if they are anxious, the plasma catecholamines will suppress into the normal range 3 hours after clonidine (noradrenaline 0.2-0.8 ng/ml, adrenaline 0.04-2 ng/ml). Phaeochromocytoma patients should not.]
- CT scan of the adrenal gland.
- Metaiodobezylguanidine (MIBG) scan - It is possible to see a mass-like structure in the adrenal gland.
