Isoflavones increase the production of calcitonin gene-related peptide (CGRP) in sensory neurons. Increased CGRP then promotes the production of insulin-like growth factor 1 (IGF-1) in tissues like skin and hair follicles. The study found that isoflavone administration in mice increased CGRP and IGF-1 levels in hair follicles and promoted hair growth and pigmentation. However, these effects were not observed in mice that lacked the CGRP gene, indicating isoflavones promote hair growth by increasing CGRP and IGF-1 levels.