Hypothalamic-pituitary-adrenal axis activity in patients with primary polydipsia compared to healthy controls.

OBJECTIVE: Primary polydipsia is characterized by excessive fluid intake which may suppress vasopressin levels. It is speculated that suppressed vasopressin levels lead to a dysregulated hypothalamic-pituitary-adrenal (HPA) axis as vasopressin co-modulates the HPA axis. However, data are contradictory. The aim of this study was to investigate markers of the HPA axis in patients with primary polydipsia compared to healthy controls. DESIGN: Exploratory analysis combining data from two different prospective observational studies. PATIENTS: We included 34 patients with primary polydipsia (68% females, median aged 29.5 years (interquartile range, IQR: 26.0, 38.8) and 20 healthy controls (55% females, median age 24.0 years [IQR: 22.0, 27.2]). MEASUREMENTS: The main outcome was difference in HPA axis activity assessed using circadian serum and salivary cortisol, 24-h urinary free cortisol and cortisol levels before and after adrenocorticotropic hormone (ACTH) stimulation; vasopressin suppression was assessed measuring fasting copeptin levels between patients with primary polydipsia and healthy controls using Wilcoxon rank-sum test. RESULTS: No difference was seen in circadian serum cortisol levels (p = .9), urinary free cortisol levels (p = .17) and serum cortisol in response to ACTH stimulation (p = .77) between groups. Circadian salivary cortisol levels were significantly lower in patients with primary polydipsia compared to healthy controls with an estimated difference of -3.7 nmol/L (95% CI: -5.5, -1.8 nmol/L, p < .001). Fasting copeptin levels were significantly lower in patients with primary polydipsia compared to healthy volunteers (p < 0.01). CONCLUSION: Our results suggest no difference in HPA axis activity between patients with primary polydipsia and healthy controls. The observed difference in salivary cortisol levels may be linked to a dilution effect in saliva rather than an altered stress axis considering the other findings.

Effects of glucagon-like peptide-1 receptor agonists on fluid intake in healthy volunteers.

PURPOSE: Glucagon-like peptide-1 (GLP-1) receptor agonists (RA) reduce appetite and energy intake. Recent findings from animal studies suggest a role of GLP-1 in drinking and water homeostasis. We aimed to elucidate whether GLP-1 RA reduce fluid intake in healthy volunteers. METHODS: Double-blind, randomized, placebo-controlled, crossover study. 20 healthy volunteers received dulaglutide 1.5 mg and placebo (0,9% sodium chloride) subcutaneously once weekly for 3 weeks. At the end of each treatment period, participants attended an 8-h evaluation visit, during which they were requested to eat two standardized meals and to drink water ad libitum. The primary outcome was the total fluid intake (ml) during the evaluation visit. RESULTS: Mean [SD] age of participants (60% female) was 27 [9.2] years. All but four participants drank less on dulaglutide versus placebo treatment despite identical food intake. The median [IQR] difference of fluid intake on dulaglutide compared to placebo treatment was -100 ml [-400-0]. Median [IQR] total fluid intake was 1300 ml [888-1600] versus 1600 ml [1000-1720], on dulaglutide and placebo treatment, p = 0.06. Median [IQR] 24-h urine output was reduced in dulaglutide versus placebo-treated participants: 1250 ml [975-2080] versus 1680 ml [1400-2040], p = 0.04. Median serum sodium levels were 140 mmol/L on both visits and no difference in thirst perception was noted. CONCLUSIONS: GLP-1 RA such as dulaglutide seem to modulate fluid balance in humans. This leads us to speculate that GLP-1 RA may be an interesting therapeutic options for patients with excessive drinking behavior e.g., primary polydipsia.

Effects of Glucagon-Like Peptide-1 Receptor Agonists on Hypothalamic-Pituitary-Adrenal Axis in Healthy Volunteers.

Context: Recent findings from animal and human studies indicate that glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) modulate stress response by activating the hypothalamic-pituitary-adrenal (HPA) axis, which may have relevant clinical implications. Objective: To investigate the influence of GLP-1 RA treatment on HPA axis activity compared with placebo in healthy volunteers. Design: Double-blind, randomized, crossover study. Setting: University Hospital Basel, Switzerland. Participants: Twenty healthy volunteers. Intervention: Dulaglutide (Trulicity®) 1.5 mg and placebo (0.9% sodium chloride) were given subcutaneously once weekly for 3 weeks. Main Outcome Measures: Twenty-four-hour urinary free cortisol, circadian rhythm of serum and salivary cortisol, cortisol after 1 mg dexamethasone suppression test, and cortisol levels before and after stimulation with ACTH. Results: Urinary free cortisol levels were similar under dulaglutide [median (interquartile range) 240 nmol/L (164, 324)] vs placebo [188 nmol/L (133, 338), P = 0.131]. The circadian rhythm of serum and salivary cortisol were comparable in both groups as were cortisol levels after dexamethasone [dulaglutide 28 nmol/L (22, 47.5) vs placebo 26.5 nmol/L (15.8, 45.5), P = 0.4]. Serum cortisol levels in dulaglutide and placebo treated participants were 522 nmol (388, 710) and 530 nmol/L (394, 747), before (P = 0.6), and 658 nmol/L (604, 810) and 636 nmol/L (512, 910) after ACTH stimulation (P = 0.87). Conclusion: Our results suggest that there is no activation of the HPA axis by long-term GLP-1 RA exposure, particularly dulaglutide, at the medically approved dosage of 1.5 mg once weekly.