Testosterone and growth hormone (GH) work through different pathways but boost each other: testosterone raises GH and IGF-1 output, and GH makes muscle more responsive to testosterone. Studies show the pair adds more lean mass than either alone, and more side effects.
- Testosterone drives muscle protein building; GH mainly shifts fat and fluid and supports connective tissue.
- Combining them raises blood sugar, fluid retention and blood pressure risks.
- Both are prescription drugs in Canada and banned in sport.
Testosterone and growth hormone are often mentioned in the same breath, but they are very different hormones. Understanding how they interact explains why people combine them, and why the combination needs more monitoring than either alone.
Two hormones, two jobs
| Testosterone | Growth hormone | |
|---|---|---|
| Made in | Testes (and a little in the adrenal glands) | Pituitary gland |
| Main effect on muscle | Increases muscle protein synthesis and fibre size | Modest lean mass, much of it water |
| Effect on fat | Reduces fat, especially in men with low T | Breaks down stored fat, especially belly fat |
| Other effects | Libido, red blood cells, bone, mood | Connective tissue, skin, sleep, bone |
| Acts through | Androgen receptor, and estradiol | IGF-1 made by the liver and tissues |
How they affect each other
- Testosterone boosts GH. Much of this happens after testosterone is converted to estradiol, which increases the size of GH pulses. Boys’ growth spurt at puberty is driven by this link.
- GH and IGF-1 help testosterone work. IGF-1 activates muscle stem cells (satellite cells), which give muscle fibres more nuclei to support growth.
- Low testosterone often comes with low IGF-1, and treating low T in men usually raises IGF-1 a little.
What studies show about combining them
The best evidence comes from a 2010 trial published in the Annals of Internal Medicine by Meinhardt and colleagues. Recreationally active young adults received GH, testosterone, both, or placebo for eight weeks. GH alone reduced fat and increased lean mass (much of it fluid) and improved sprint capacity slightly, but not strength or endurance. The combination in men produced the largest increase in lean mass and sprint capacity, with more side effects.
Studies in older men with low hormones found similar results: more lean mass and less fat with the combination, but more fluid retention, joint pain and carpal tunnel symptoms, and some showed blood sugar problems.
The added risks
Each hormone has its own side effects, and some of them stack:
- Fluid retention and blood pressure. Both hormones cause the body to hold sodium and water.
- Blood sugar. GH reduces insulin sensitivity; supraphysiological testosterone can worsen cholesterol and metabolic health.
- Heart. High-dose androgens can thicken the heart muscle and raise LDL cholesterol; long-term excess GH also enlarges the heart. See steroids and cholesterol.
- Red blood cells. Testosterone raises hematocrit, which thickens the blood.
- Cell growth. High IGF-1 promotes the growth of all cells. Anyone with cancer, or a history of it, should not use GH.
- Fertility. Testosterone shuts down sperm production; GH does not reverse this.
Bloodwork to watch
If both hormones are in use, a broader panel than usual is worth getting:
- Total testosterone and estradiol
- IGF-1
- Complete blood count (hematocrit and hemoglobin)
- Fasting glucose and HbA1c
- Lipid panel, liver enzymes and kidney function
- Blood pressure, measured at home with a validated cuff
Your family doctor can order these, or you can pay privately at LifeLabs or Dynacare. Our bloodwork guide explains timing and normal ranges.
Gentler ways to support both
Natural testosterone and GH both respond to the same habits: enough deep sleep, resistance training, staying lean, managing alcohol, and treating sleep apnea if present. Men with symptoms of low testosterone should get tested; treatment through a doctor is widely available in Canada. See hormone therapy vs steroid cycles for the difference between medical TRT and performance use.
Legal status in Canada
Testosterone is a Schedule IV controlled substance under the Controlled Drugs and Substances Act, and growth hormone is a prescription drug. Both are banned in sport. Products on our site, including testosterone enanthate and human growth hormone, list their specifications and lab results on each page.
Frequently asked questions
Does testosterone increase growth hormone?
Yes, modestly. Much of the effect comes from testosterone being converted to estradiol, which increases growth hormone pulses.
Is HGH or testosterone better for muscle?
Testosterone has a much stronger effect on muscle size and strength. Growth hormone mostly adds lean mass as fluid and reduces fat.
What blood tests should I get if using both?
Testosterone, estradiol, IGF-1, a complete blood count, fasting glucose or HbA1c, cholesterol, and liver and kidney function.
Photo: rawpixel (public domain).
General information, not medical advice. Testosterone and growth hormone are prescription drugs in Canada; use them only under medical supervision.
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