Dihydrotestosterone Inhibits Hair Growth in Mice by Inhibiting Insulin-Like Growth Factor-I Production in Dermal Papillae

The study demonstrated that dihydrotestosterone (DHT) inhibits hair growth in mice by reducing insulin-like growth factor-I (IGF-I) production in dermal papillae. This reduction is mediated by the suppression of sensory neuron stimulation, as evidenced by decreased release of calcitonin gene-related peptide (CGRP) from dorsal root ganglion neurons. Administration of DHT decreased dermal levels of CGRP, IGF-I, and IGF-I mRNA, and inhibited hair re-growth, effects that were reversed by the androgen receptor antagonist flutamide or by administering CGRP. The study involved groups of five mice for each experimental condition and used histological and mRNA analysis, immunohistochemical staining, and assessment of cell proliferation to reach its conclusions. The findings suggest that DHT contributes to hair loss by inhibiting sensory neuron stimulation and reducing IGF-I production, which is essential for hair growth.