Impact of overnight dexamethasone suppression on the adrenal androgen response to an oral glucose tolerance test in women with and without polycystic ovary syndrome

In order to test the hypothesis that adrenocortical overactivity, possiblyrelated to the stress of testing, may impact on the measurement ofcirculating androgen concentrations during glucose- inducedhyperinsulinaemia, we prospectively screened 10 patients with thepolycystic ovary syndrome (PCOS) and nine healthy control women with anoral glucose tolerance test (OGTT), before and after the administration ofdexamethasone. Blood sampling was performed at 0, 30, 60, 90, and 120 minfollowing the oral ingestion of 75 g of glucose, before and after theadministration of 1.0 mg dexamethasone on the evening prior to testing.Total and free testosterone, androstenedione, dehydroepiandrosterone(DHEA), DHEA sulphate (DHEAS), cortisol, glucose and insulin were assessedduring the 2 h OGTT. Women with PCOS had increased basal concentrations offree testosterone, total testosterone, androstenedione, and insulincompared to control women. In women with PCOS an acute decline incirculating concentrations of DHEAS occurred during the OGTT. In PCOS womenthere were no changes in other ovarian or adrenal androgens during OGTTbefore or following dexamethasone administration. In control women DHEAconcentrations declined during the OGTT. Following overnight dexamethasonesuppression in control women, circulating concentrations of DHEAS andtestosterone also declined. It is concluded that: (i) in PCOS women onlythe concentration of circulating DHEAS decreased during glucose-inducedhyperinsulinaemia and dexamethasone administration did not further alterandrogen responses to an OGTT; (ii) it is possible that, in thesehyperandrogenic patients, the insulin-related suppression of adrenocorticaltestosterone and DHEA is negated by their much greater ovarian secretion ofthese androgens; (iii) in control women DHEA concentrations acutelydeclined during the OGTT and the administration of dexamethasone resultedin the acute decline of DHEA, DHEAS, and testosterone; (iv) it appears thatthe stress related to testing impacts on the androgen response to OGTT, atleast in healthy women.