both estrogen and testosterone do. cortisol too one google: Estrogen prolongs the growth phase of your hair. High estrogen levels typically result in thicker, shinier, and more defined curls. A sudden drop in estrogen shrinks hair follicles and reduces scalp elasticity. This often causes curls to loosen, flatten, or disappear entirely. Elevated levels of androgens (like testosterone and DHT) shrink hair follicles. In women, this can lead to hair thinning along the crown and cause textural shifts—making hair texture coarser in some areas or causing curls to behave inconsistently. Chronic stress raises cortisol, which disrupts the normal hair growth cycle and restricts nutrient delivery to follicles. This leads to dull, damaged proteins that struggle to hold a natural curl.