Gender differences in scalp hair growth rates are maintained but reduced in pattern hair loss compared to controls.

Background: Hair loss is related to follicular density, programmed regrowth and hair productivity. Objective: The dissatisfaction with hair growth in patients experiencing hair loss might be due to slower linear hair growth rate (LHGR). Methods: LHGR and hair diameter was evaluated in Caucasian controls and patients with patterned hair loss employing the validated non-invasive, contrast-enhanced-phototrichogram with exogen collection. Results: We evaluated 59,765 anagen hairs (controls 24,609, patients 35,156) and found thinner hairs grew slower than thicker hairs. LHGR in normal women was generally higher than in normal men. LHGR correlates with hair diameter (P < 0.006) and global thinning is associated with slower growth rates. Compared with hair of equal thickness in controls, subjects affected with patterned hair loss showed reduced hair growth rates, an observation found in both male and female patients. Males with pattern hair loss showed further reduction in growth rates as clinical severity worsened. However, sample size limitations prevented statistical evaluation of LHGR in severely affected females. Limitations: Caucasian ethnicity. Conclusion: In pattern hair loss, LHGR significantly contributes to the apparent decrease in hair volume in affected areas. In early onset, LHRG might have a prognostic value in females but not in males.