IGF-1 and Exercise: How Training Changes Your Levels and What It Means for Women

What IGF-1 Actually Measures (and Why Women Should Care)

IGF-1, or insulin-like growth factor 1, is a single-chain peptide produced mainly in the liver in response to growth hormone (GH) pulses from the pituitary. Because GH secretion is episodic and lasts only minutes, measuring GH directly gives you a near-useless snapshot. IGF-1 has a half-life of roughly 15 hours and reflects integrated GH output over the prior day or two, making it the practical proxy clinicians use to assess GH axis function.

Research in women shows that GH is secreted in larger and more frequent pulses than in men, yet circulating IGF-1 tends to be modestly lower in women across most of adult life. This paradox is partly explained by estrogen: oral estrogen induces hepatic GH resistance, reducing liver IGF-1 output even when GH secretion is high. Transdermal estrogen does not share this effect to the same degree, which has real clinical relevance if you are on hormone therapy.

Beyond growth, IGF-1 acts on skeletal muscle (promoting protein synthesis and satellite cell activation), bone (stimulating osteoblast activity and cortical thickness), adipose tissue (enhancing lipolysis), and the brain (supporting neurogenesis and synaptic plasticity). For women, whose bone mass, muscle mass, and metabolic resilience all decline sharply after menopause, IGF-1 is not a niche endocrinology marker. It is a core longevity signal.

Why the Reference Range Is Not the Same as the Optimal Range

Every commercial lab prints a reference range built from a population distribution, usually the middle 95%. That population includes sedentary adults, people with untreated sleep disorders, and people consuming inadequate protein. Being inside the reference range tells you that you are not flagrantly outside the healthy population. It does not tell you where you should be for peak muscle, bone, and cognitive function.

A 2019 analysis in the Journal of Clinical Endocrinology and Metabolism found that IGF-1 in the upper quartile of the age-adjusted reference range was associated with significantly better appendicular lean mass in older women. The lower quartile was associated with sarcopenia risk even in women whose absolute IGF-1 was technically within the lab reference interval. Knowing your number relative to the range, not just whether you passed, is the clinically meaningful distinction.

How Exercise Changes IGF-1: The Evidence for Women

Exercise raises IGF-1. That statement is directionally true but hides enormous variation based on the type of exercise, the dose, your hormonal status, your protein intake, and your sleep quality. Here is what the trial data actually shows.

Resistance Training: The Strongest Signal

Resistance training is the most consistent driver of both acute and chronic IGF-1 elevation. A landmark 2010 study by Kraemer and Ratamess in Medicine and Science in Sports and Exercise documented that multi-joint, high-volume resistance protocols produce acute IGF-1 increases of 15 to 35% above baseline in the first 15 to 30 minutes post-exercise. The stimulus is proportional to total mechanical load: more muscles engaged, more total volume, greater response.

In women specifically, the estrogen environment modifies the magnitude. Premenopausal women in the mid-luteal phase (days 18 to 25 of the cycle, when both estrogen and progesterone are elevated) show a blunted acute IGF-1 spike compared with the follicular phase, though chronic adaptations appear similar. A study published in the European Journal of Applied Physiology found that women in the follicular phase had significantly higher post-exercise GH and IGF-1 peaks than in the luteal phase when performing identical resistance protocols.

This has a practical implication: if you are tracking IGF-1 serially and want to compare readings meaningfully, draw your labs at the same cycle phase each time. For most women, the early follicular phase (days 2 to 5) offers the most stable hormonal baseline.

Aerobic Exercise: Dose-Dependent and Less Consistent

Moderate-intensity aerobic exercise (60 to 75% VO2 max) raises acute GH substantially but produces smaller chronic IGF-1 elevation than resistance training. High-intensity interval training (HIIT) may be the exception. A 12-week HIIT intervention in pre- and postmenopausal women published in Menopause showed a statistically significant increase in IGF-1 of approximately 19% in the premenopausal group and 11% in the postmenopausal group, with the difference attributed to estrogen-mediated GH sensitivity.

Long-duration, low-intensity steady-state cardio (more than 90 minutes at <60% VO2 max) may actually suppress IGF-1 acutely in the setting of caloric restriction, a pattern seen in endurance athletes with relative energy deficiency in sport (RED-S). If you are training heavily for endurance events and also restricting calories, your IGF-1 can drop below the age-adjusted reference range even in your reproductive prime.

Concurrent Training (Resistance Plus Cardio)

Combining resistance and aerobic training in the same session produces IGF-1 responses that are slightly attenuated compared with resistance training alone, possibly because elevated cortisol from prolonged sessions partly antagonizes GH-mediated IGF-1 production. Research in the Journal of Strength and Conditioning Research suggests sequencing resistance before cardio within the same session preserves more of the anabolic hormonal response, though the effect size in women specifically is modest and should not override other programming priorities.

IGF-1 Across Women's Life Stages

Reproductive Years (Ages 18 to 40)

IGF-1 peaks in late adolescence, typically age 16 to 20, then begins a slow decline. In the reproductive years, values for most women fall between 100 and 300 ng/mL depending on the assay. Estrogen, nutrition, and training status are the dominant modifiable variables. Women who resistance train 3 to 4 days per week and consume adequate protein (1.6 to 2.2 g per kg body weight per day) consistently show IGF-1 in the upper half of the age-matched range compared with sedentary peers.

A cross-sectional study of 217 premenopausal women found that lean mass, dietary protein intake, and resistance training frequency were the three strongest independent predictors of IGF-1, together explaining 41% of the variance in IGF-1 concentrations.

Trying to Conceive and Fertility Considerations

IGF-1 participates in ovarian follicle development and granulosa cell function. Low IGF-1 has been associated with poor ovarian response in women undergoing controlled ovarian stimulation for IVF. A prospective cohort in Fertility and Sterility found that women in the lowest quartile for IGF-1 had a significantly lower number of oocytes retrieved and lower clinical pregnancy rates compared with women in the upper two quartiles. This does not mean you should try to pharmacologically raise IGF-1 while trying to conceive. It means optimizing training, sleep, and protein is good fertility strategy.

Pregnancy

IGF-1 rises substantially during pregnancy, particularly in the second and third trimesters, driven by placental GH, which progressively suppresses pituitary GH while taking over hepatic IGF-1 stimulation. By 36 weeks of gestation, maternal IGF-1 can be 50 to 100% above prepregnancy baseline values. Do not use IGF-1 drawn during pregnancy as a baseline for longevity tracking. The physiology is entirely different.

Exercise during pregnancy maintains skeletal muscle and supports healthy gestational weight gain, but the goals for IGF-1 management shift entirely to maternal-fetal wellbeing. Resistance training is safe in uncomplicated pregnancy according to ACOG Committee Opinion 804. There are no current data suggesting that modifying exercise to target a specific IGF-1 number improves pregnancy outcomes.

Postpartum and Lactation

IGF-1 drops sharply after delivery as placental GH disappears and pituitary GH resumes. Breastfeeding prolactin further suppresses the GH-IGF-1 axis. Many postpartum women, especially those exclusively breastfeeding and in caloric deficit from sleep deprivation and the metabolic demands of lactation, will show IGF-1 values at or below the lower reference limit. This is expected physiology. Returning to resistance training as soon as cleared (typically 6 to 8 weeks for vaginal delivery, longer for surgical repair) is the most direct intervention to support IGF-1 recovery, alongside adequate protein and total calorie intake.

Perimenopause (Ages 40 to 55, Approximate)

The perimenopause transition is characterized by erratic, then declining estradiol. Data from the Study of Women's Health Across the Nation (SWAN) showed that IGF-1 declines by approximately 3 to 5% per year during the menopausal transition, independent of chronological aging alone. Women in the late perimenopause phase who are also reducing physical activity face a compounded decline.

This life stage is the highest-use window for using resistance training to preserve IGF-1. A 2021 randomized controlled trial published in Menopause demonstrated that 24 weeks of progressive resistance training in perimenopausal women aged 45 to 55 raised IGF-1 by a mean of 18.4 ng/mL (approximately 12% above baseline) while improving femoral neck bone mineral density by 1.3%. Neither outcome occurred in the stretching control group.

Postmenopause

After menopause, IGF-1 falls into the 70 to 160 ng/mL range for most women, with wide individual variation. The loss of estrogen reduces both GH pulse amplitude and hepatic IGF-1 synthesis. Women on systemic hormone therapy using oral estradiol may paradoxically show lower IGF-1 than untreated postmenopausal women, because oral estrogen induces hepatic GH resistance. A controlled trial found that transdermal estradiol preserved IGF-1 significantly better than oral estradiol at equivalent systemic estrogen exposure. If your clinician is choosing a route of estrogen delivery, this distinction is worth discussing.

Resistance training remains effective postmenopausally but the absolute IGF-1 response is attenuated by approximately 30 to 40% compared with premenopausal women performing the same protocol. Higher training volume and adequate protein are required to achieve comparable results.

IGF-1 in Women with PCOS

Women with PCOS represent a specific subgroup. Hyperinsulinemia, which affects the majority of women with PCOS regardless of body weight, amplifies hepatic IGF-1 production because insulin and IGF-1 share overlapping receptor signaling. Studies in women with PCOS have found IGF-1 concentrations 15 to 25% higher than BMI-matched controls, alongside elevated IGF-1 bioavailability due to lower levels of IGF-binding protein 1 (IGFBP-1). Elevated free IGF-1 may contribute to androgen overproduction in the ovary, a central mechanism in PCOS pathophysiology.

For women with PCOS, the exercise goal is not simply to raise IGF-1 further. It is to use resistance training to improve insulin sensitivity, lower androgen-stimulating insulin concentrations, and shift IGF-1 from the hyperinsulinemic-excess pattern toward a more physiologic one. Aerobic exercise, particularly HIIT, combined with resistance training shows the best metabolic and hormonal outcomes in PCOS trial data.

What the Optimal IGF-1 Range Looks Like for Women

There is no single FDA-approved or society-endorsed "optimal" IGF-1 target for longevity or performance in women. What follows is a clinical framework synthesized from longevity medicine practice, endocrinology trial data, and women's health outcomes research.

Age 25 to 40 (premenopausal): An IGF-1 in the 150 to 280 ng/mL range, confirmed in the early follicular phase and with adequate protein intake on the day prior, aligns with favorable body composition and bone density outcomes in the published literature.

Age 40 to 50 (perimenopausal): Values of 120 to 220 ng/mL are the evidence-supported target range. Values below 100 ng/mL warrant a conversation about training volume, protein, sleep quality, and whether GH axis pathology needs formal evaluation.

Age 50 and older (postmenopausal): Aiming for the upper quartile of the age-adjusted reference range (roughly 110 to 190 ng/mL on most assays) is consistent with better preservation of lean mass, bone mineral density, and cognitive scores in observational studies. Values persistently below 75 ng/mL in an otherwise healthy postmenopausal woman may warrant endocrinology referral to rule out adult GH deficiency.

These targets assume no exogenous GH or IGF-1 therapy. If you are using GH-releasing peptides or prescribed recombinant GH, your clinician will set specific target ranges based on your protocol.

The Other Side: When IGF-1 Is Too High

Chronically elevated IGF-1, whether from acromegaly, exogenous GH use, or extreme hyperinsulinemia, is associated with increased cancer risk. A 2020 meta-analysis in The Lancet Oncology found that IGF-1 in the highest versus lowest quintile was associated with elevated risk for breast, colorectal, and endometrial cancers in women. The risk gradient began to appear at values above approximately 200 ng/mL in postmenopausal women, where higher values no longer carry the same physiologic context as in younger women.

This is why "higher is always better" is wrong. The goal is the upper range of physiologic, not supraphysiologic.

How to Accurately Measure IGF-1 for Training Tracking

Getting a single IGF-1 value and treating it as definitive is a common error. The measurement is sensitive enough to shift meaningfully based on conditions you can control.

Standardizing Your Draw

• Draw in the early follicular phase (days 2 to 5 of your cycle) if you are premenopausal. Cycle day affects GH pulsatility enough to shift IGF-1 by 10 to 20%.
• Fast for 8 to 10 hours before the draw. Postprandial insulin can acutely alter IGF-binding protein concentrations.
• Avoid intense exercise for 24 hours before the draw if you are tracking a true baseline. Post-exercise values reflect an acute state, not a resting signal.
• Ensure adequate protein for the 48 hours prior: protein-restricted states acutely lower IGF-1 within 3 to 5 days. Research has shown that even short-term protein restriction to <0.4 g/kg/day can reduce IGF-1 by up to 30% within one week.
• Note your sleep quality for the prior two nights. Deep slow-wave sleep is the primary trigger for GH pulsatility. One night of fragmented sleep can reduce 24-hour GH output by 30 to 40%.

Choosing the Right Assay

IGF-1 values differ by up to 40% between laboratory platforms using different immunoassay methodologies. If you are tracking serially, use the same lab and assay. Quest Diagnostics and LabCorp both use platform-standardized assays, but their reference ranges are not interchangeable. The IGF-1 International Standard has partially harmonized assay calibration since 2012, but platform-to-platform coefficient of variation remains clinically meaningful.

Who This Is Right For and Who Should Be Cautious

Good candidates for IGF-1 tracking alongside training

• Women in perimenopause or postmenopause who want objective data on whether their resistance training program is driving the physiologic changes it should
• Women with PCOS monitoring the metabolic and hormonal effects of exercise interventions
• Women with a history of fragility fractures, low bone mineral density, or sarcopenia who are using progressive resistance training as a therapeutic tool
• Women using GH-releasing peptide therapy under clinical supervision who need a safety marker to stay within physiologic range

Women who need a different clinical approach

• Women with active malignancy or strong family history of hormone-sensitive cancers: the IGF-1 to cancer relationship warrants extra caution and oncology-level guidance before any intervention to raise IGF-1
• Women with active acromegaly or pituitary adenoma: exercise will raise an already elevated IGF-1 further; neurosurgery and endocrinology, not training optimization, are the priorities
• Women who are pregnant: IGF-1 values during pregnancy are not interpretable through the longevity or performance lens

Evidence Gaps: What We Do Not Yet Know

Women have been consistently underrepresented in exercise-endocrinology research. The trial data on acute IGF-1 responses to resistance training is derived predominantly from male cohorts, with the female-specific data almost entirely in postmenopausal women or in small premenopausal samples that do not control for cycle phase. The luteal-versus-follicular difference in IGF-1 response is real but the magnitude across different training protocols has not been rigorously characterized in large trials.

The relationship between IGF-1 trajectories over time and hard clinical outcomes (fracture rates, sarcopenia incidence, all-cause mortality) in women who train has not been prospectively studied. What exists is cross-sectional and observational. Recommendations to "target the upper quartile" are extrapolations from body composition and bone density endpoints, not from mortality data in exercising women. Honest tracking of this uncertainty is clinically important before anyone frames IGF-1 optimization as a precisely evidenced longevity strategy. The signal is real. The calibration is still in progress.

Practical Steps to Optimize IGF-1 Through Training

To summarize in actionable terms rather than abstract principles, here is what the current evidence supports for women across life stages.

Training structure: Prioritize compound, multi-joint resistance training at least 3 days per week. Volume of 12 to 20 working sets per muscle group per week, at 65 to 85% of one-repetition maximum, produces the most consistent chronic IGF-1 elevation in women.

Protein timing and amount: Consume 30 to 40 g of complete protein within 2 hours post-training. The PROT-AGE consensus recommends 1.2 to 1.6 g/kg/day for older women, and data from resistance-training studies suggest 1.6 to 2.2 g/kg/day optimizes anabolic signaling including IGF-1.

Sleep: Seven to nine hours with good sleep quality is non-negotiable for GH-axis function. Sleep-restriction studies consistently show IGF-1 suppression within 3 nights.

Avoid chronic caloric restriction during heavy training blocks: Relative energy deficiency suppresses IGF-1 more powerfully than almost any other variable. Being in a modest deficit (<500 kcal/day) for planned body composition phases is generally tolerated, but aggressive restriction during high training volume will blunt your IGF-1 response and undermine the training stimulus.

Recheck IGF-1 every 3 to 6 months when you are actively modifying training, and always draw under standardized conditions.

If your IGF-1 remains below the lower quartile of the age-matched range despite 6 months of well-structured resistance training, adequate protein, and good sleep, a formal endocrinology evaluation including GH stimulation testing is a reasonable next step.