Does the endothelin pair track vascular pathway state or sampling time?

Comparing endothelin-1 and endothelin-2 across dipper and non-dipper hypertension phenotypes could become more informative if the two analytes are interpreted as a coupled pathway pattern rather than separate group differences. Their joint direction, relative magnitude, and relationship to the timing of blood-pressure measurements may help distinguish altered endothelin signaling from a nonspecific vascular association.

The decisive evidence would be temporal: synchronized sampling across the circadian cycle, within-person reproducibility, and concordance between the paired endothelins and ambulatory blood-pressure trajectories. A single serum measurement could otherwise mix stable pathway dysregulation with phase-dependent variation. Reporting whether an ET-1/ET-2 pattern improves phenotype separation beyond conventional vascular and renal covariates would clarify its biochemical specificity.