1st-order laboratory parameters-obligatory laboratory tests.
- Small blood count
- Urine status (rapid test for: pH, protein, glucose), sediment if necessary; test for microalbuminuria (excretion of small amounts of albumin (20 to 200 mg/l or 30 to 300 mg per day) with urine).
- Renal parameters – uric acid, urea, creatinine if necessary creatinine clearance.
- Electrolytes (blood salts) – such as calcium, sodium, potassium, magnesium, phosphate.
- Fasting glucose (fasting blood glucose) – and if necessary glucose tolerance test (oGTT) – detection of previously undetected diabetes mellitus.
- Blood lipids – cholesterol, LDL (low density lipoprotein), HDL (high density lipoprotein), triglycerides – to assess cardiovascular risk.
- TSH (thyroid-stimulating hormone) – to exclude hyperthyroidism (hyperthyroidism).
- Γ-GT (gamma-glutamyl transferase) – indication of alcohol abuse.
- Urinalysis for albumin and blood (erythrocytes (red blood cells/hemoglobin) [microalbuminuria 30-300 mg/24 hours, albumin-creatinine ratio: males ≥ 22 mg/g creatinine (≥ 2.5 mg/mol), females 31 mg/g creatinine (≥ 3.5 mg/mol); safely normal up to 10 mg/g creatinine]* .
Laboratory parameters 2nd order – depending on the results of the history, physical examination, etc. – for differential diagnostic clarification.
- 24h-collection urine with determination of.
- Creatinine [calculated glomerular filtration rate (< 60 ml/min/1.73 m2) or creatinine clearance < 60 ml/min]
- Cortisol – if Cushing’s syndrome/hypercortisolism (renal cortical hyperfunction with elevated cortisol) is suspected.
- Metanephrine and catecholamines – in suspected pheochromocytoma.
- Metanephrines and normetanephrines in plasma – in suspected pheochromocytoma (usually benign tumor, predominantly originating in the adrenal glands).
- Dexamethasone inhibition test – screening test for suspected Cushing’s syndrome/hypercortisolism.
- Findings: plasma cortisol < 5 µg/dl on 2 mg dexamethasone short-term test excludes Cushing’s syndrome.
- Aldosterone–renin quotient* – screening test for suspected primary hyperaldosteronism (Conn syndrome) (caveat: falsely high value with beta blocker use, falsely negative values with spironolactone).
- Confirmatory test by saline stress test or fludrocortisone suppression test, if necessary; and
- Adrenal CT (computed tomography) and serial blood sampling from the adrenal veins, if necessary.
- PTH (parathyroid hormone)
- Potassium* – due toindication of primary/secondary hyperaldosteronism [elevation of plasma and urinary aldosterone in hypokalemia].
* Values in square brackets for early hypertensive end organ damage.
Further notes
- Arterial hypertension may have up to 10% endocrine causes. Younger and refractory patients should therefore also be evaluated for endocrine causes of hypertension.
- Primary hyperaldosteronism should always be initially ruled out in patients with arterial hypertension >150/100 mm Hg (see below * ).