stimulation test
A stimulation test is a way of asking a gland, 'Can you step up when called upon?' Instead of reading a single resting level, the clinician gives a deliberate trigger and then measures whether the gland responds by pouring out more hormone. It is the endocrine equivalent of revving an engine to see if it can reach full power, not just idle.
Such tests are most useful when a hormone deficiency is suspected, because a low baseline level can be ambiguous — it might be normal for that moment. By administering a stimulus and watching for a sufficient rise, the test reveals whether the gland has reserve capacity. A blunted or absent response confirms that the gland (or the chain of signals feeding it) is failing.
The stimulus can be the natural commanding hormone, a synthetic analog of it, or a physiological stress that the body answers by releasing the hormone. Because some of these challenges can provoke side effects, stimulation tests are run under controlled conditions with timed blood draws, and the response is judged against established cutoffs rather than ordinary reference ranges.
In an insulin tolerance test, controlled hypoglycemia is induced to stress the body; a healthy pituitary should respond by sharply raising growth hormone and ACTH.
A stimulation test probes hormonal reserve, usually to diagnose deficiency.
The classic example is the ACTH (cosyntropin) stimulation test for adrenal insufficiency: synthetic ACTH is injected, and a healthy adrenal cortex should raise cortisol above a threshold within 30–60 minutes.