Growth hormone response to thyrotrophin releasing hormone in women with polycystic ovarian syndrome

Abstract

Recent clinical studies have suggested that women with polycystic ovarian syndrome (PCOS) may have disturbances of growth hormone (GH) kinetics and the GH/insulin-like growth factor (IGF)-I system. The knowledge that in various metabolic abnormalities there is a paradoxical sensitivity of pituitary somatotrophs to thyrotrophin-releasing hormone (TRH) administration led to this investigation of the GH secretory response to TRH in women with PCOS. Twenty-four women with PCOS and 18 control women were studied. TRH was given as a single i.v. injection (time 0) and blood samples for GH measurements were obtained at -15, 0, 15, 30, 60 and 90 min. The GH responses were expressed as the area under the curve (AUC) or the differences from the basal value (Δmax). The GH response to TRH (mean ± SEM) was greater in women with PCOS (Δmax 2.47 ± 1.73 versus 0.47 ± 0.05 ng/ml, P < 0.05 and GH AUC 8.05 ± 2.10 versus 2.58 ± 0.18 ng/ml/90 min, P < 0.05). According to GH response to TRH, two PCOS subgroups were identified: (i) normal responders (n = 14) who showed Δmax GH response (0.36 ± 0.06 ng/ml) and GH AUC (1.93 ± 0.64 ng/ml/90 min) similar to that in the controls and (ii) over-responders (n ± 10) who showed a paradoxical increase in GH concentrations in response to TRH (Δmax GH response 5.43 ± 1.27 ng/ml and GH AUC 16.62 ± 3.51 ng/ml per 90 min) that was significantly higher than in normally responding PCOS patients (P < 0.0001) or in controls (P < 0.0001). These data demonstrate an enhanced GH response to TRH administration in a subgroup of women with PCOS.