glutathione in lungs Lung and oxidative stress: implications cigarette smoke-induced airway disease | American Journal of Physiology-Lung Cellular and Molecular Physiology Glutathione S-transferases and their implications

Unfortunately, your body's ability to produce glutathione naturally decreases with age, typically starting around age 20 and declining by approximately 1% per year

So, in the context of glutathione, the reduced form is referring to cysteines sulfur atom keeping its electrons to itself (Figure 2)

10.1016/j.neurobiolaging.2009.11.016 115 TocilescuM

Adv Exp Med Biol (2015) 803:2939

Protein thiol homeostasis: Glutathione maintains proteins in their reduced (functional) state through S-glutathionylation, a reversible post-translational modification that regulates protein activity under oxidative stress [2]

Cysteine and L-Methionine - Amino acids known to thicken hair