Urinary Cortisol ELISA

Cortisol is a steroid hormone released from the
adrenal cortex in response to an hormone called
ACTH (produced by the pituitary gland), it is involved
in the response to stress; it increases blood pressure, blood sugar levels, may cause infertility in women,
and suppresses the immune system. Cortisol acts through specific intracellular receptors
and has effects in numerous physiologic systems,
including immune function, glucose-counter
regulation, vascular tone, substrate utilization and
bone metabolism. Cortisol is excreted primarily in
urine in an unbound (free) form.
Cortisol is bound, in plasma, from corticosteroid- binding globulin (CBG, transcotin), with high affinity,
and from albumin. Only free cortisol is available to
most receptors.
These normal endogenous functions are the basis for
the physiological consequences of chronic stress - prolonged cortisol secretion causes muscle wastage,
hyperglycaemia, and suppresses immune /
inflammatory responses. The same consequences
arise from long-term use of glucocorticoid drugs.
The free cortisol fraction represents the metabolically
active cortisol. In normal conditions, less then 1% it
comes excrete in urines. In pathological conditions
(syndrome of Cushing) the levels of free urinary
cortisolo are elevate, because the CBG don’t bound
the plasmatic cortisol in excess and it was remove
with urines.
During pregnancy or estro-progestogen treatment an
increase of plasmatic cortisol caused by an increment
of the production of the transport protein, but the
levels of free urinary cortisol results normal to indicate
a correct surrenic functionality.
This test is very useful to estimate the real surrenic
function, because is dose the free cortisol, it is the
metabolically active form. Moreover the measurement
of free urinary cortisolo is the better parameter for the
diagnosis of the Cushing’s syndrome.