To determine whether circulating levels of GDF15 among patients with PAI differed significantly from those of healthy volunteers, we compared GDF15 and cortisol measurements from patients with PAI due to Addison’s disease in cohort 1 (male n = 6, female n = 4, age 46.4 ± 9.4 years, BMI 25.6 ± 2.5 kg/m2) to a matched control group from the healthy volunteer study (male n = 6, female n = 4, age 43.6 ± 11.7 years, BMI 25.4 ± 3.6 kg/m2). The gene discussed is GDF15; the disease is primary adrenal insufficiency.