FSHR and diabetes mellitus: Diabetes and its associated oxidative stress, by increasing the level of free radicals, and affecting LH and FSH receptors, reduce serum testosterone levels (Tirabassi et al., 2016 ▶) and with a negative feedback effect to adjust the serum testosterone level, the secretion of LH and FSH from the pituitary gland increases (Guyton and Hall, 2020 ▶).