Corticotropin and cortisol response to maximal exercise testing in central diabetes insipidus

Effect of Arginine on the Hypothalamic-Pituitary-Adrenal Axis in Individuals With and Without Vasopressin Deficiency

CONTEXT

Arginine stimulates pituitary hormones, like growth hormone and vasopressin, but its effect on the hypothalamic-pituitary-adrenal (HPA) axis is unknown. Arginine may also stimulate the HPA axis, possibly through a mechanism involving vasopressin.

OBJECTIVE

To investigate the effect of arginine on adrenocorticotropic hormone (ACTH) and cortisol in subjects with and without vasopressin deficiency.

DESIGN

Prospective study, University Hospital Basel.

PARTICIPANTS

38 patients with central diabetes insipidus, 58 patients with primary polydipsia, and 50 healthy controls.

INTERVENTION

Arginine infusion with measurement of ACTH, cortisol and copeptin at baseline and 30, 45, 60, 90, and 120 minutes.

RESULTS

We found different response patterns to arginine: in patients with diabetes insipidus (and low stimulated copeptin levels) median (interquartile range [IQR]) ACTH and cortisol increased from 22.9 (16.8, 38.7) to 36.6 (26.2, 52.1) ng/L and from 385 (266, 463) to 467 (349, 533) nmol/L, respectively. In contrast, median (IQR) ACTH and cortisol levels decreased in patients with primary polydipsia (despite high stimulated copeptin levels): ACTH from 17.3 (12.3, 23) to 14.8 (10.9, 19.8) ng/L and cortisol from 343 (262, 429) to 272 (220.8, 360.3) nmol/L; likewise, in healthy controls: ACTH from 26.5 (17.6, 35.7) to 14.8 (12.1, 22.7) ng/L and cortisol from 471 (393.3, 581.8) to 301.5 (206.5, 377.8) nmol/L.

CONCLUSION

Diabetes insipidus is associated with increased responsiveness of ACTH/cortisol to arginine. In contrast, arginine does not stimulate the HPA axis in healthy controls or in primary polydipsia.

Copeptin concentrations during psychological stress: the PsyCo study

OBJECTIVE

The prognostic/diagnostic biomarker copeptin, an arginine vasopressin surrogate, reflects physical stress. Whether copeptin concentration increases upon psychological stress is unknown. We investigated psychological stress effects on copeptin secretion in healthy volunteers and patients with central diabetes insipidus (DI).

DESIGN

A prospective observational study was conducted to study the relation between copeptin concentration and psychological stress.

METHODS

A total of 20 healthy adults (ten female) and eight patients with central DI (four female) underwent the Trier Social Stress Test including, in order, 30-min waiting period, 10-min anticipation period, 10-min test period and 40-min recovery. Serum copeptin and cortisol concentrations and self-rated stress component feelings were determined in the pre-/post-anticipation period, post-test period and twice post-recovery.

RESULTS

In healthy volunteers, the median (25th-75th percentile) copeptin concentration peaked immediately during the post-test period at 5.1 (3.2-7.0) pmol/l, vs 3.7 (2.6-5.4) pmol/l at baseline. Over the measurement course, copeptin concentration significantly elevated (coefficient; 95% CI) (0.14; 0.06-0.23, P=0.002). The important predictors of increase in copeptin concentration were feelings of tension (0.06; 0.04-0.08, P<0.001) and avoidance (0.07; 0.04-0.10; P<0.001). Copeptin and cortisol levels were associated (0.43; 0.13-0.72, P<0.005). Patients with DI had lower baseline concentrations (1.55 (1.2-3.1) pmol/l) when compared with healthy volunteers, P=0.006. Patients with DI showed no increase upon psychological stress (peak 2.15 pmol/l (1.5-2.28), P=0.79). By contrast, cortisol values were similar in patients and volunteers.

CONCLUSIONS

In healthy volunteers, copeptin levels significantly increased after psychological stress testing; this response was blunted in patients with DI.