We also describe the key mechanisms regulating Hb expression and functionality under hypoxic stress and highlight the significant role of Hb in neurodegenerative diseases, such as stroke, traumatic brain injury, Parkinson’s disease, Alzheimer’s disease, and amyotrophic lateral sclerosis, in which hypoxia is a key pathological feature. The gene discussed is GSTM1; the disease is early-onset autosomal dominant Alzheimer disease.