Review · Energy and healthy aging

HGH Activator review: can one amino acid capsule raise growth hormone after 50?

HGH Activator from NatureCast is sold as a natural way to switch your own growth hormone back on. We read the human studies behind its amino acids, including the ones the sales page cites, and looked for the label.

By Grant Whitaker, Editor · Updated October 23, 2026 · 15 studies checked on PubMed

What HGH Activator is

HGH Activator is a capsule supplement from NatureCast Products, a company based in Coral Springs, Florida. The bottle shows 30 capsules, and the directions on the sales page are one capsule a day. It is sold on the NatureCast website through Digistore24 in 1, 3 and 6-bottle packages, as a one-time purchase. NatureCast says it is not sold in stores or on other websites.

The sales page is aimed at adults over 40, men and women, and promises firmer muscles, less body fat, smoother skin, more energy and a better sex life. The idea behind it: growth hormone falls with age, injections are expensive and risky, and a blend of amino acids can prompt your pituitary gland to release more of its own. The product contains no hormone. It is a dietary supplement made of amino acids.

Why growth hormone is the hook, and why that matters

The sales page leans on a 1990 study in the New England Journal of Medicine. In it, 12 healthy men aged 61 to 81 with low IGF-1 (a marker of growth hormone activity) received injections of biosynthetic human growth hormone three times a week for six months. They gained 8.8% lean body mass and lost 14.4% fat mass, while 9 untreated men did not change ^[1].

Two things are worth knowing about that study. First, it tested prescription hormone injections, which raised IGF-1 into the youthful range. HGH Activator contains no hormone, and nothing in that study tells us what amino acid capsules do. Second, later research put the injection results in context. A Stanford systematic review of 18 study populations of healthy older adults (mean age 69) found growth hormone shifted about 2.1 kg from fat to lean mass, did not change body weight or bone density, and raised the rates of swelling, joint pain, carpal tunnel syndrome and breast tissue growth in men. Its conclusion was that growth hormone cannot be recommended for healthy older adults ^[2].

So even the real hormone produced modest gains with real side effects. The question for HGH Activator is narrower: can its amino acids raise your own growth hormone enough to matter?

The formula, and the missing label

We could not find a Supplement Facts panel for HGH Activator anywhere: not on the current sales page, not on the older NatureCast product page, not on the order forms and not in the affiliate materials. The bottle images show the front of the label only. Without that panel we cannot tell you how much of each ingredient a capsule contains, so we do not guess.

The current sales page names these ingredients: ornithine alpha-ketoglutarate (OKG), L-ornithine HCl, L-arginine, L-lysine, glycine and L-glutamine. An older NatureCast page for the same product also lists colostrum with 30% IgG, which the current page does not mention. We could not confirm which list matches the bottles shipping today, and that mismatch is itself a finding.

There is also a simple physical limit. All of these ingredients have to fit in one capsule a day. Common capsule sizes hold roughly half a gram to a gram of powder in total. The studies below used grams of a single amino acid per dose.

The formula next to the research

Arginine and lysine: a short spike in the young, no change in older men

The sales page builds its case on a 1981 Italian study. In 15 male volunteers, a single oral dose of 1,200 mg lysine plus 1,200 mg arginine triggered growth hormone release, while neither amino acid did much on its own at the same dose ^[4]. That is a real finding, but it was a one-dose, qualitative test, and the abstract describes plain arginine and does not give the "10 times" comparison the sales page quotes.

The study that speaks most directly to men over 50 came from the Gerontology Research Center in Baltimore. Eight healthy men around 69 years old took 3 g of arginine plus 3 g of lysine twice a day for 14 days, and eight similar men took placebo. Arginine and lysine did not change growth hormone measured through the night, the response to a stimulation test, or IGF-1. The authors concluded that oral arginine and lysine is not a practical way to raise growth hormone over time in older men ^[3]. That is a dose many times larger than anything a single capsule could contain, over the same "couple of weeks" the sales page says is enough to see changes.

Arginine: dose matters, and so does timing

In eight young men aged 18 to 33, single doses of 5 g and 9 g of arginine raised growth hormone for about an hour or two. A 13 g dose did not raise it further and caused considerable stomach upset in most of the men ^[5]. A follow-up by the same team found that 7 g of arginine taken before a weight workout actually produced a smaller growth hormone response than the workout alone ^[6]. A review of amino acids used by athletes reached a similar view: oral doses big enough to raise growth hormone tend to cause stomach discomfort and diarrhea, and no well-run study showed bigger gains in muscle or strength from taking them ^[7].

Arginine plus ornithine: a study in trained athletes

The sales page cites a Polish trial in which 9 experienced strength athletes took arginine and ornithine during three weeks of heavy training and 8 took placebo. The supplemented group had higher growth hormone and IGF-1 after exercise ^[8]. Resting hormone levels did not differ between groups, and the study did not measure muscle, fat or energy. It tells us little about a man in his sixties taking one capsule a day.

Glycine and glutamine: single-dose rises

In a 1978 study, 19 healthy adults drank 250 mL of a 0.3 molar glycine solution (about 5.6 g of glycine), and growth hormone rose ^[9]. An older NatureCast page describes a "250 milligram" glycine dose from this line of research; the abstract we read describes 250 milliliters of solution, which is a very different amount. In another small study, 2 g of glutamine in a drink raised growth hormone 90 minutes later in 9 healthy people ^[10].

The closest trial to an everyday supplement tested 5 g of a glycine, glutamine and niacin mix twice a day for three weeks in 42 adults aged 40 to 76. Growth hormone rose about 70% compared with placebo, but IGF-1 did not change, and mood and memory did not improve ^[11]. That is a 10 g daily dose, again far beyond one capsule.

OKG and ornithine

Ornithine alpha-ketoglutarate is a compound of ornithine and alpha-ketoglutarate. A 2010 review describes it as a precursor of glutamine, arginine and proline that raises insulin and growth hormone secretion, with anabolic effects shown mainly in people losing muscle because of illness. The author presents it as a possible area for future research in aging, not an established result ^[12]. We found no trial of OKG for energy or body composition in healthy older men.

What the marketing claims vs. what we could verify

• "The lysine and arginine combination makes it 1000% more effective." We could not trace this figure to a publication. The 1981 study supports the idea that the pair works better together than apart for a single dose in younger men ^[4], and the trial in older men found no effect after two weeks ^[3].
• Visible changes "within as little as a couple of weeks." We found no study of HGH Activator itself, and no trial showing that oral amino acids change appearance, muscle or fat in older adults in that time.
• Sexual benefits for men and women. The review the sales page cites says the role of growth hormone in sexual function is not fully understood and mostly comes from studies of people with hormone disorders ^[13]. It does not test any amino acid supplement.
• The 1990 NEJM results. Those came from hormone injections ^[1], and a later systematic review advised against growth hormone for healthy older adults ^[2].

To be fair to the vendor, its own page carries a disclaimer that the cited studies were not done on this product and may have used different amounts. Our point is the same one, stated plainly.

Price, packages and refund policy

One bottle holds 30 capsules, a 30-day supply. Prices on the NatureCast sales page when we checked:

• 6 bottles: $29.95 each ($179.70 total), listed with free shipping. About $1 a day.
• 3 bottles: $52.33 each ($156.99 total), plus shipping.
• 1 bottle: $59, plus shipping.

When we opened the Digistore24 order forms (without ordering), each one, including the 6-bottle form, showed a $14.95 shipping and handling line. That may depend on your country, so check the total before you pay.

The sales page promises a 180-day refund, even on empty bottles. The fine print differs between pages: NatureCast's refund policy page says the refund includes shipping, while its terms page says the guarantee covers the product price only. If you order, keep your receipt and ask support which terms apply.

Safety

The ingredients are amino acids found in food, and the amount in one capsule is likely small. Still, a few points are worth raising with your doctor, especially if you take medication:

• Blood pressure. A meta-analysis of 11 placebo-controlled trials (4 to 24 g a day) found arginine lowered blood pressure by about 5 points systolic and 3 points diastolic ^[14]. If you take blood pressure medicine or other drugs that lower blood pressure, ask before adding arginine.
• After a heart attack. In the VINTAGE MI trial, 153 people recovering from a first heart attack took arginine (goal dose 3 g three times a day) or placebo for six months. Arginine did not improve heart measures, 6 people in the arginine group died versus none on placebo, and the trial was stopped early. The authors advised that arginine should not be recommended after a heart attack ^[15].
• Stomach upset. Large oral amino acid doses commonly cause stomach discomfort and diarrhea ^{[5] [7]}.
• Dairy. If the current formula still contains colostrum, it is a milk product. People with a milk allergy should confirm with the seller first.

Because the label is not published, you cannot show your doctor or pharmacist the exact doses. Ask NatureCast for the Supplement Facts panel before you start. Results vary from person to person, and new or worsening symptoms deserve medical care.

What we liked and what gave us pause

Frequently asked questions

Does HGH Activator contain growth hormone?

No. According to NatureCast it contains amino acids and no hormones. It is a dietary supplement, not a hormone therapy, and it should not be confused with prescription growth hormone.

Can amino acids raise growth hormone?

Large single doses of arginine, glycine or glutamine have raised growth hormone for an hour or two in small studies, mostly in younger adults ^{[5] [9] [10]}. In older men, two weeks of arginine and lysine at 12 g a day combined did not change growth hormone or IGF-1 ^[3]. A short rise in a blood test is also different from a change in muscle, fat or energy.

Where can I buy HGH Activator?

On the NatureCast sales page, with checkout handled by Digistore24. NatureCast says it is not sold in stores or on other sites.

How long should I try it?

Results vary. If you try it, decide in advance what you will judge it on (energy, training, sleep) and use the refund window if you notice nothing. Training and protein intake will likely matter more for strength and body composition than any capsule.

How we reviewed HGH Activator

We read the current and older NatureCast sales pages, the refund and terms pages, the Digistore24 order forms (without ordering) and the vendor's affiliate materials, and we looked for a Supplement Facts label. We then searched PubMed for human studies of each listed amino acid and growth hormone, opened every study the sales page cites that is indexed there, and added the trials most relevant to men over 50. We did not test the product on people, and nobody at Stark Verve is a medical professional. Read our editorial policy to learn how we choose and update reviews. Stark Verve earns a commission if you buy through our links; that never changes what we write about the evidence.