Pregnancy. Most pregnant women develop stretch marks by the end of their pregnancy. The physical stretching of the skin, along with hormonal factors, likely plays a role.
Weight gain.
Stretch marks sometimes occur during substantial weight gain. Weightlifters can develop stretch marks, particularly on the arms. Adolescents may notice stretch marks during growth spurts.
Medication use.
Corticosteroid creams, lotions and pills and chronic use of oral or systemic steroids can cause stretch marks.
Conditions or diseases.
Cushing's syndrome and adrenal gland diseases can cause widespread stretch marks, as can Marfan syndrome, Ehlers-Danlos syndrome and other hereditary (genetic) disorders.