IGF-1

Insulin-like growth factor-1 — the dermal-papilla growth factor that drives follicle proliferation and prolongs anagen (the active growth phase).

“Table 2 gives, for males aged 20 years, 2.5th-97.5th percentile IGF-1 of 133.1-430.0 ng/mL (50th percentile 258.5 ng/mL).” males, 20

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 20 years, 2.5th-97.5th percentile IGF-1 of 107.8-416.0 ng/mL (50th percentile 234.8 ng/mL).” females, 20

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 21-25 years, 2.5th-97.5th percentile IGF-1 of 115.2-354.8 ng/mL (50th percentile 217.2 ng/mL).” males, 21-25

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 21-25 years, 2.5th-97.5th percentile IGF-1 of 92.9-342.0 ng/mL (50th percentile 196.2 ng/mL).” females, 21-25

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 26-30 years, 2.5th-97.5th percentile IGF-1 of 97.9-281.6 ng/mL (50th percentile 176.8 ng/mL).” males, 26-30

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 26-30 years, 2.5th-97.5th percentile IGF-1 of 78.4-270.0 ng/mL (50th percentile 158.7 ng/mL).” females, 26-30

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 31-35 years, 2.5th-97.5th percentile IGF-1 of 88.3-246.0 ng/mL (50th percentile 156.4 ng/mL).” males, 31-35

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 31-35 years, 2.5th-97.5th percentile IGF-1 of 73.1-243.0 ng/mL (50th percentile 144.7 ng/mL).” females, 31-35

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 36-40 years, 2.5th-97.5th percentile IGF-1 of 83.4-232.7 ng/mL (50th percentile 147.9 ng/mL).” males, 36-40

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 36-40 years, 2.5th-97.5th percentile IGF-1 of 69.0-227.0 ng/mL (50th percentile 135.7 ng/mL).” females, 36-40

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 41-45 years, 2.5th-97.5th percentile IGF-1 of 74.9-216.4 ng/mL (50th percentile 135.7 ng/mL).” males, 41-45

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 41-45 years, 2.5th-97.5th percentile IGF-1 of 61.5-204.4 ng/mL (50th percentile 121.7 ng/mL).” females, 41-45

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 46-50 years, 2.5th-97.5th percentile IGF-1 of 66.9-205.1 ng/mL (50th percentile 125.7 ng/mL).” males, 46-50

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 46-50 years, 2.5th-97.5th percentile IGF-1 of 56.8-194.5 ng/mL (50th percentile 114.5 ng/mL).” females, 46-50

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 51-55 years, 2.5th-97.5th percentile IGF-1 of 60.6-200.3 ng/mL (50th percentile 119.4 ng/mL).” males, 51-55

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 51-55 years, 2.5th-97.5th percentile IGF-1 of 53.0-189.6 ng/mL (50th percentile 109.9 ng/mL).” females, 51-55

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 56-60 years, 2.5th-97.5th percentile IGF-1 of 54.3-194.2 ng/mL (50th percentile 112.5 ng/mL).” males, 56-60

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 56-60 years, 2.5th-97.5th percentile IGF-1 of 45.6-172.4 ng/mL (50th percentile 98.0 ng/mL).” females, 56-60

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 61-65 years, 2.5th-97.5th percentile IGF-1 of 48.8-187.7 ng/mL (50th percentile 106.0 ng/mL).” males, 61-65

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 61-65 years, 2.5th-97.5th percentile IGF-1 of 42.2-169.0 ng/mL (50th percentile 94.1 ng/mL).” females, 61-65

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 66-70 years, 2.5th-97.5th percentile IGF-1 of 46.5-191.9 ng/mL (50th percentile 105.8 ng/mL).” males, 66-70

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 66-70 years, 2.5th-97.5th percentile IGF-1 of 38.3-162.5 ng/mL (50th percentile 88.7 ng/mL).” females, 66-70

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 71-75 years, 2.5th-97.5th percentile IGF-1 of 40.9-179.2 ng/mL (50th percentile 96.7 ng/mL).” males, 71-75

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 71-75 years, 2.5th-97.5th percentile IGF-1 of 36.6-164.7 ng/mL (50th percentile 88.2 ng/mL).” females, 71-75

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 76-80 years, 2.5th-97.5th percentile IGF-1 of 37.1-172.0 ng/mL (50th percentile 91.1 ng/mL).” males, 76-80

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 76-80 years, 2.5th-97.5th percentile IGF-1 of 34.7-164.8 ng/mL (50th percentile 86.7 ng/mL).” females, 76-80

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 81-85 years, 2.5th-97.5th percentile IGF-1 of 33.8-165.4 ng/mL (50th percentile 86.1 ng/mL).” males, 81-85

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 81-85 years, 2.5th-97.5th percentile IGF-1 of 34.4-172.4 ng/mL (50th percentile 89.1 ng/mL).” females, 81-85

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for males aged 86-90 years, 2.5th-97.5th percentile IGF-1 of 32.2-166.1 ng/mL (50th percentile 85.0 ng/mL).” males, 86-90

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

“Table 2 gives, for females aged 86-90 years, 2.5th-97.5th percentile IGF-1 of 33.6-177.8 ng/mL (50th percentile 90.3 ng/mL).” females, 86-90

Reference Intervals for Insulin-like Growth Factor-1 (IGF-I) From Birth to Senescence: Results From a Multicenter Study Using a New Automated Chemiluminescence IGF-I Immunoassay Conforming to Recent International Recommendations · The Journal of Clinical Endocrinology & Metabolism · 2014 DOI 10.1210/jc.2013-3059 · PMID 24606072

Blocks the hormone that shrinks follicles lowers 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 raises 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 raises 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

It raises 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 lowers 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 raises Hair.

10.3390/cimb47090773. doi 10.3390/cimb47090773

It lowers Growth hormone.

10.3389/fendo.2024.1456195 — It is a thermostat, not a one-way pathway. doi 10.3389/fendo.2024.1456195

It raises 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 lowers 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 raises 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 raises 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 raises 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 lowers 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

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