Clinical endocrinology
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Clinical endocrinology · Sep 2005
Comparative StudySalivary cortisol determined by enzyme immunoassay is preferable to serum total cortisol for assessment of dynamic hypothalamic--pituitary--adrenal axis activity.
The aim of this study was to determine whether salivary cortisol measured by a simple enzyme immunoassay (EIA) could be used as a surrogate for serum total cortisol in response to rapid changes and across a wide range of concentrations. ⋯ Comparisons of matched salivary and serum samples in response to dynamic hypothalamic-pituitary-adrenal (HPA) axis testing. Subjects Healthy women (n=10; three taking oral oestrogens) and men (n=2), aged 23--65 years, were recruited from the community. Measurements Paired saliva and serum samples were obtained during three protocols: 10 min of exercise at 90% of maximal heart rate (n=8), intravenous administration of corticotrophin-releasing hormone (CRH; n=4), and dexamethasone suppression (n=7). Cortisol was measured in saliva using a commercial high-sensitivity EIA and total cortisol was measured in serum with a commercial radioimmunoassay (RIA). Results The time course of the salivary cortisol response to both the exercise and CRH tests paralleled that of total serum cortisol. Salivary cortisol demonstrated a significantly greater relative increase in response to the exercise and CRH stimuli (697+/- 826%vs. 209+/- 150%, P=0.04 saliva vs. serum). A disproportionately larger increase in free cortisol, compared with total, would be expected when the binding capacity of cortisol-binding globulin (CBG) is exceeded. In response to dexamethasone suppression, relative decreases in cortisol were not significantly different between the two media (-47+/- 56%vs.-84+/- 8%, P=0.13 saliva vs. serum). Although a significant linear correlation was found for all paired salivary and serum total cortisol samples (n=183 pairs, r=0.60, P<0.001), an exponential model provided a better fit (r=0.81, P<0.001). The linear correlations were strengthened when data from subjects on oral oestrogens (n=52 pairs, r=0.75, P < 0.001) were separated from those not taking oestrogens (n=131 pairs, r=0.67, P<0.001). Conclusions Salivary cortisol measured with a simple EIA can be used in place of serum total cortisol in physiological research protocols. Evidence that salivary measures represent the biologically active, free fraction of cortisol includes: (1) the greater relative increase in salivary cortisol in response to tests that raise the absolute cortisol concentration above the saturation point of CBG; (2) the strong exponential relationship between cortisol assessed in the two media; and (3) the improved linear correlations when subjects known to have increased CBG were analysed separately. Thus, an advantage of measuring salivary cortisol rather than total serum cortisol is that it eliminates the need to account for within-subject changes or between-subject differences in CBG.
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Clinical endocrinology · Sep 2005
Effect of gender and gonadal status on the long-term response to somatostatin analogue treatment in acromegaly.
:GH and IGF-I secretion is related to gender and age. ⋯ The results of this study demonstrate that long-term responsiveness to OCT-LAR is similar in women and men. Care should be taken in women with acromegaly and hypogonadism treated with somatostatin analogues and oral oestro-progestinic as in this case GH levels are higher while IGF-I levels are lower than after the somatostatin analogues alone.