Insulin‐like growth factor‐1, (IGF-1, has a central role in hair cycle control and hair shaft differentiation in developing hair follicles. IGF‐1 is established to promote hair follicle growth via regulation of cellular proliferation. Anagen(growing) hair quickly enters into catagen (shedding) in the absence of IGF‐1. Moreover, IGF‐1 receptor knockout mice exhibit a marked reduction in the quantity of hair follicles, and atypical diffusely thinned follicular patterns.
  DP cells from balding scalp follicles secreted almost six times less IGF‐1 than those from non‐balding scalps.

Insulin‐like growth factor‐1: roles in androgenetic alopeciaAbstractOf all the cytokines or growth factors that have been postulated to play a role in hair follicle, insulin‐like growth factor‐1 (IGF‐1) is known to be regulated by androgens. However, how IGF‐1 is altered in the balding scalp has not yet been investigated. In this study, expressions of IGF‐1 and its binding proteins by dermal papilla (DP) cells obtained from balding versus non‐balding hair follicles were quantified using growth factor array. DP cells from balding scalp follicles were found to secrete significantly less IGF‐1, IGFBP‐2 and IGFBP‐4 (< 0.05) than their non‐balding counterparts. Our data confirmed that the downregulation of IGF‐1 may be one of the important mechanisms contributing to male pattern baldness.

Existing evidence demonstrates that raising IGF-1 levels in human subjects with androgenetic alopecia produces a reliable hair growth effect.
Both Propecia (finasteride) and Soy Isoflavones have been shown to do just that.
Dietary isoflavone increases insulin-like growth factor-I production, thereby promoting hair growth in mice
The expression of insulin-like growth factor 1 in follicular dermal papillae correlates with therapeutic efficacy of finasteride in androgenetic alopecia
When Soy Isoflavones are combined with capsaicin, the effects on IGF-1 and hair growth become even more pronounced. Capsaicin is the active ingredient in chili peppers. Dr Harada, in the following landmark study, demonstrated significant hair growth in 64.5 % of subjects with Androgenetic Alopecia.

Growth Horm IGF Res      2007 Oct;17(5):408-15Administration of capsaicin and isoflavone promotes hair growth by increasing insulin-like growth factor-I production in mice and in humans with alopeciaNaoaki Harada1Kenji OkajimaMasatoku AraiHiroki KuriharaNaomi Nakagata  AbstractObjective: Insulin-like growth factor-I (IGF-I) plays an important role in hair growth. Capsaicin activates vanilloid receptor-1, thereby increasing the release of calcitonin gene-related peptide (CGRP) from sensory neurons, and CGRP has been shown to increase IGF-I production. We recently reported that isoflavone, a phytoestrogen, increases production of CGRP by increasing its transcription in sensory neurons. These observations raise the possibility that administration of capsaicin and isoflavone might promote hair growth by increasing IGF-I production. In the present study, we examined this possibility in mice and humans with alopecia.
Design: Dermal IGF-I levels, immunohistochemical expression of IGF-I in the skin and hair regrowth were examined after capsaicin and isoflavone administration to wild-type (WT) mice and CGRP-knockout mice. Plasma levels of IGF-I and promotion of hair growth were evaluated in 48 volunteers with alopecia after administration of capsaicin and isoflavone for 5 months.
Results: Subcutaneous administration of capsaicin significantly increased dermal IGF-I levels at 30 min after administration in WT mice (p < 0.01), but not in CGRP-knockout mice. Dermal levels of IGF-I were significantly higher in WT mice administered capsaicin and isoflavone for 4 wks than in those administered capsaicin alone for 4 wks (p < 0.01) and in those administered neither of them (p < 0.01). Immunohistochemical expression of IGF-I at dermal papillae in hair follicles was increased in WT mice administered capsaicin and isoflavone and in those administered capsaicin alone at 4 wks. Hair regrowth was clearly more accelerated in WT mice administered capsaicin and isoflavone for 4 wks than in those administered capsaicin alone for 4 wks and in those administered neither of them. Plasma levels of IGF-I were significantly increased from baseline levels in 31 volunteers with alopecia at 5 months after oral administration of capsaicin (6 mg/day) and isoflavone (75 mg/day) (p < 0.01), while they were not increased in 17 volunteers with alopecia administered placebo. The number of volunteers with alopecia who showed promotion of hair growth at 5 months after administration was significantly higher among volunteers administered capsaicin and isoflavone (20/31: 64.5%) than among those administered placebo (2/17: 11.8%) (p < 0.01).
Conclusions: These observations strongly suggested that combined administration of capsaicin and isoflavone might increase IGF-I production in hair follicles in the skin, thereby promoting hair growth. Such effects of capsaicin and isoflavone might be mediated by sensory neuron activation in the skin.

Interestingly, DHT, the main androgen implicated in pattern hair loss, has been demonstrated to inhibit IGF-1.
Dihydrotestosterone inhibits hair growth in mice by inhibiting insulin-like growth factor-I production in dermal papillae
We have received numerous positive anecdotal reports from those who have tried the combination of Soy Isoflavone Extract and Cayenne Pepper. You can try this as a standalone treatment or easily integrate these compounds into an existing hair growth regime by simply using 2 capsules of Super Absorbable Soy Isoflavones and one rounded teaspoon of cayenne pepper, which will yield 80 mg. of Isoflavones (slightly exceeding that used in the study) and  8.5 mg of capsaicin, which approximates the amount used in the study ( 7.92 mg).