GSTM1 and hypothyroidism: All RBC indices [hemoglobin (Hb), RBC count, hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC)] were significantly lower in patients with hypothyroidism compared to those in the control group (p ≤ 0.05), except for red blood cell distribution width (RDW), which was significantly higher in patients with hypothyroidism (p = 0.000).