Figure 14. Patterns of plasma AVP and thirst responses to hypertonic stress in patients with adipsic syndromes. Normal range responses to osmolar stimulation are shown by the shaded areas. The 4 types of adipsic syndrome are demonstrated. Patients with the Type A syndrome osmoregulate around a higher osmolar set point, while those with the Type B syndrome mount AVP and thirst responses but with reduced sensitivity. Patients with the Type C syndrome have much reduced or absent AVP and thirst responses to osmolar stimulation. Those with the Type D syndrome demonstrate normal AVP responses to osmolar stimulation but much reduced thirst responses.