(A) Calf muscle apparent tissue sodium (²³Na MRI) in FHHt (n = 84) and individuals acting as healthy controls (HCs, n = 85). (B) Representative ²³Na MRI images; calibration phantoms (10–100 mM NaCl) are labeled. (C) Th1 polarization and Th17/Th1 ratio (3-day PBMC stimulation), with representative FACS plots (D). (E) Th17 polarization and Th17/Th1 ratio as well as (G) supernatant IL-17 concentration (7-day stimulation), with representative FACS plots (F) in FHHt and HCs. (H) Th17 and Th1 polarization, Th17/Th1 ratio, and supernatant IL-17 concentration in HC cells cultured with and without +40 mM NaCl. (I) Th17 polarization and Th17/Th1 ratio in patients with FHHt on (n = 8) and off (n = 8) thiazide. (J) Th17 polarization in patients with FHHt and HCs (n = 8) with hydrochlorothiazide (20 μM), NaCl (40 mM), or both (7-day stimulation). (K) IFN-γ expression and Th1 polarization vs. urinary calcium/creatinine. (L) IL-17 vs. fractional excretion of chloride in FHHt. Red lines represent the upper limit of normal. Dots represent individuals. Red symbols denote patients with FHHt off thiazide. Groups in A, C, E, and G were compared by 2-tailed Mann-Whitney test; in H by paired Wilcoxon test; and in K and L by Spearman’s correlation. Bars show the median and IQR. *P < 0.05, **P < 0.01. Data in B, D, and F represent 9, 26, and 26 experiments, respectively.