Clinical endocrinology
-
Clinical endocrinology · Jan 1998
Randomized Controlled Trial Clinical TrialBright light exposure and pituitary hormone secretion.
Exposure to bright light inhibits melatonin secretion in man. As the relationship between melatonin and pituitary function remains controversial, we investigated the effect of altering the melatonin rhythm by bright light during the early hours of darkness on pituitary hormone secretion in man. ⋯ Exposure to bright light during the early hours of darkness delays the nocturnal melatonin peak and alters cortisol, GH, PRL and nocturnal vasopressin secretion, while modification of the sleep pattern decreases vasopressin concentrations and alters its nocturnal peak.
-
Clinical endocrinology · Jan 1998
A very high dose dexamethasone suppression test for differential diagnosis of Cushing's syndrome.
The high-dose dexamethasone (dex) suppression test of cortisol secretion (8 x 2 mg dex over two days or 8 mg overnight) is a mainstay in the differential diagnosis of Cushing's syndrome (CS). In some patients with pituitary Cushing's disease (CD), however, plasma cortisol is not suppressed to < 50% of control by 8 mg of dex. We therefore hypothesized that a higher dose of dex might produce more effective suppression of cortisol secretion in CD. ⋯ In this series, the hCRH test was the most reliable test for the differential diagnosis of Cushing's syndrome. The 32 mg dexamethasone test with measurement of urinary free cortisol was clearly superior to the 8 mg test and to other aspects of the very high dose dexamethasone test. It can be recommended for 'non-suppressible' patients with ACTH-dependent Cushing's syndrome and can be performed on outpatients.