The reasoning: ADH opens the door; the loop provides the gradient
AVP (supraoptic and paraventricular nuclei → posterior pituitary) rises from a plasma osmolality threshold ≈ 280–285 mOsm/kg; thirst starts slightly higher (~290–295). Non‑osmotic stimuli: ≥ ~8–10% fall in effective arterial volume/pressure (baroreceptor‑mediated, can override hypotonicity), nausea, pain, hypoxia, stress, drugs (SSRIs, carbamazepine, cyclophosphamide, vincristine, opioids, MDMA). Inhibited by ethanol, hypo‑osmolality, ANP.