Growth factor
You want it up: IGF-1 sustains the hair growth phase, and androgens work partly by suppressing it.
In depth
Insulin-like growth factor-1 — the dermal-papilla growth factor that drives follicle proliferation and prolongs anagen (the active growth phase).
What drives it
Blocks the hormone that shrinks follicles reduces it.
DHT suppresses dermal-papilla IGF-1 production (Zhao 2011, Growth Horm IGF Res, PMID 21839661) by lowering cgrp / androgen-receptor signaling — an androgen route into follicle miniaturization. The intermediate is named and it is a microRNA: the androgen receptor directly promotes transcription of miR-221, which suppresses IGF-1 expression, inactivating mapk in dermal papilla cells and PI3K/akt in dermal sheath cells. In aga patients miR-221 correlated positively with AR and negatively with IGF-1, and miR-221 suppressed hair growth and dpc/dsc proliferation (PMC10367565). Therapeutic link: IGF-1 expression in follicular dermal papillae correlates with the therapeutic efficacy of finasteride — the marker tracks who responds to the drug. PMID 21839661 · PMC10367565
Growth hormone increases it.
IGF-1 is how most of growth hormone's message is delivered: GH is secreted by the anterior pituitary and acts on peripheral organs to stimulate IGF-1 production, with the liver supplying about 75% of circulating IGF-I; the Igf1 gene is a principal target of GH activation (PMC4075164, Endotext NBK279056). More GH does not automatically mean more IGF-1. Direction depends on the endpoint. PMC4075164
Adenosine A2B receptor increases it.
Adenosine upregulates IGF-1 gene expression in cultured dermal papilla cells alongside FGF-7 and FGF-2. gene-expression endpoint in cultured human cells. Iino 2007, J Invest Dermatol 127(7):1825. PMID 17301835
What it drives
It increases Growth restraint.
IGF-1 binding to IGF-1R recruits IRS-1 and PI3K, activating Akt and then mTORC1 — the canonical anabolic route that raises muscle protein synthesis (PMC7564605). With the existing mTOR→muscle edge this wires IGF-1’s hypertrophy effect mechanistically rather than as a shortcut. mTOR activity is also tightly regulated by amino acid availability independently of this arm, and mTORC1 vs mTORC2 differ -- Raptor-deficient muscle becomes dystrophic while Rictor knockout muscle is indistinguishable from wild type. Mouse + C2C12 myotubes. PMC7564605
It reduces Calms inflammation.
IGF-1/Akt signaling inhibits the atrophy-inducing NF-κB and Smad/myostatin pathways in skeletal muscle (PMC7564605) — IGF-1 is anti-catabolic as well as anabolic. the review states the role of IGF-1 in atrophy specifically is less clear than its hypertrophy role, and IGF-1/PI3K/Akt signaling falls during denervation, unloading and immobilization -- so the protective arm is itself lost in the conditions where it is most needed. PMC7564605
It increases Hair.
10.3390/cimb47090773. doi 10.3390/cimb47090773
It reduces Growth hormone.
10.3389/fendo.2024.1456195 — It is a thermostat, not a one-way pathway. doi 10.3389/fendo.2024.1456195
It increases Muscle.
The expert sarcopenia reviews named IGF-1 decline as a mechanism; IGF-1/MGF is also named as a primary anabolic route. The protective arm is excellent and the title says it: muscle-specific expression of IGF-1 blocks angiotensin II-induced skeletal muscle wasting. IGF1 transgenic mice ARE resistant to atrophy from angiotensin OR cardiac cachexia, and local IGF1 injection is sufficient to block disuse atrophy. Mechanistically measured: marked increase in mTOR and p70S6K phosphorylation, and the angiotensin-induced fall in phospho-Akt completely blocked. And the conditional is the commercially important half: IGF-1 is not what makes muscle grow under load. Overload hypertrophy was unchanged in mice overexpressing a dominant-negative IGF1 receptor. Take the receptor out of action and loading still works. A second null, in the same disease the positive result claims: in hindlimb-unloaded MLC/mIgf-1 mice, surprisingly, IGF-1 overexpression was unable to counteract the loss of muscle weight and the decrease of fiber cross-sectional area. Local injection blocks disuse atrophy in one report and transgenic overexpression fails to in another. Both are recorded. And a baseline oddity: MLC/mIgf-1 mice have muscle hypertrophy not accompanied by increased Akt phosphorylation at rest — the textbook intermediate sits flat while the outcome moves (doi 10.1172/JCI22324; doi 10.1152/physiol.00041.2007; PMC3670938; PMC3143906). Verbatim: “IGF-1 increases skeletal muscle protein synthesis via PI3K/Akt/mTOR and PI3K/Akt/GSK3β pathways”. doi 10.1172/JCI22324 · PMC3670938
It reduces Cell turnover.
IGF-1 also inhibits apoptosis, prolongs the follicular growth phase, and boosts VEGF expression. In hair specifically it prevents follicular cell apoptosis, and in human hair organ culture it prevents follicles entering a catagen-like state — which, given that catagen is programmed apoptosis, is the same statement twice. Structural: the IGF-1 → Hair Growth link and the Apoptosis → Hair Growth link are both drawn. This edge says part of the first runs through the second, rather than beside it. PMID 41020895 · PMC12468416
It increases Vessel growth signal.
IGF-1 boosts VEGF expression, which supports microcirculation and nutrient delivery to hair follicles, and it promotes VEGF expression, enhancing angiogenesis around the hair follicle. IGF-1 to hair and VEGF to hair are both drawn; this link says the first is partly upstream of the second rather than parallel to it. PMID 41020895 · PMC12468416
It increases Recovery.
10.3390/cells9091970 — Recovery is assembled from the sarcopenia and VO2max literatures; none of the papers cited studied recovery itself. doi 10.3390/cells9091970
It increases Cellular aging.
The sign is deliberate and contested. IGF-1 is drawn as increasing cellular aging, not reducing it: reduced insulin/IGF-1 signaling extends lifespan across species and is the canonical 'deregulated nutrient sensing' hallmark. Yet igf1 is drawn as beneficial to muscle, bone and recovery on this same map. doi 10.1016/j.molmet.2023.101755 · PMC12293478
It reduces Prostate health.
The finding that unifies all three nodes is that the same androgen does opposite things in different tissues: testosterone acts directly, and indirectly through intracellular conversion to dihydrotestosterone by 5-alpha reductase, as in prostate cells, and separately through estrogen effect when converted to estradiol by aromatase. Raise testosterone and you also raise DHT and estradiol - which is why the same intervention supports male hormonal health and can enlarge the prostate. And the clinical data shows both arms at once: in 183 men over 50 with BPH, testosterone was significantly lower in patients with severe LUTS (285.94 ng/dL) than mild (544.09 ng/dL) - so low testosterone tracks with worse urinary symptoms, while DHT drives the gland. That is not a contradiction to resolve, it is two different molecules. Bidirectionality is explicit: the relationship between hypogonadism and metabolic disorders is bidirectional, and a vicious circle between the two components has been documented. PMC6669361
It increases Joint comfort.
10.2147/JIR.S316756 — The aging outcome lists the thirteen hallmarks themselves, each mapped to its pathway and labeled with its hallmark number. (from the reviews of this outcome). doi 10.2147/JIR.S316756
It increases Wound healing.
The one measured finding among them is the periodontal-anemia link: a meta-analysis of sixteen studies on hemoglobin and iron metabolism in periodontitis, whose authors call the association still controversial and ask for larger cohorts. (PMC7005133; doi 10.1152/japplphysiol.00971.2016; PMC12673670). Verbatim: “IGF-1 signaling improved the epithelialization and vascularization of wounds”. doi 10.1152/japplphysiol.00971.2016 · PMC7005133
It increases Clear skin.
C. acnes promotes inflammation via TLR2 and TLR4; TLR signals induce NF-kB-dependent expression of NLRP3, pro-IL-18 and pro-IL-1beta. Androgens raise sebum secretion, triggering acne. doi 10.21037/atm-22-1362 · PMC2904443
It increases Supports young eyes.
the promotion of increased insulin-like growth factor-1 (IGF-1) and decreased insulin-like growth factor binding protein-3 (IGFBP-3) action in scleral fibroblasts could contribute to the axial elongation of…. 10.1016/j.mehy.2016.01.009. doi 10.1016/j.mehy.2016.01.009
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.