Stretch marks are common among women who are past puberty. They appear as linear, thinned skin most often found on the breasts, abdomen, hips and thighs. Stretch marks may appear due to stretching of the skin or due to hormonal changes, mainly during pregnancy. They appear like scar tissue when seen under a microscope.
Stretch marks may occur due to increased cortisol secretion: The hormone produced by the adrenal glands or due to increased body mass. It is most common during pregnancy as the rapid growth of the baby and increased body mass lead to stretched skin. Taking some medications such as corticosteroids like prednisone may also produce stretch marks.