Assesses mineralocorticoid activity in potassium disorders
Laboratory Inputs
Required (1–300)
Required (1–10)
Required (50–1400)
Required (250–380)
—TTKG
Context
TTKG
Interpretation
Normal diet
8–9
Normal aldosterone activity
Hyperkalemia
< 5
Hypoaldosteronism or aldosterone resistance
Hyperkalemia
> 7
Extra-renal cause of hyperkalemia
Hypokalemia
< 2
Extra-renal K loss (GI losses, poor intake)
Hypokalemia
> 4
Renal K wasting (hyperaldosteronism, diuretics)
TTKG = (UK / PK) / (Uosm / Posm)
Prerequisite: Uosm > Posm (urine must be hypertonic to plasma)
Reflects cortical collecting duct K secretion relative to aldosterone activity
Limitations: TTKG validity requires urine osmolality > plasma osmolality. Reliability questioned in some studies. Best used as one component of the workup alongside aldosterone/renin levels. Does not apply in acute renal failure with anuria/oliguria.
