Growth hormone (GH) is made by the pituitary gland, a small gland at the base of the brain. It is not released evenly through the day. It comes in bursts, and the biggest bursts come within minutes of falling into deep sleep, mostly in the night.¹

In adults, the main job of GH is to manage how your body uses fuel. GH tells your liver to make another hormone called IGF-1 (insulin-like growth factor 1), and many of the effects of GH work through IGF-1.¹

How your body controls it, in three steps

1. Brain. A part of your brain called the hypothalamus sends a signal that switches GH release on, and another that switches it off. A hormone from your stomach, called ghrelin, also switches it on.¹
2. Pituitary. The pituitary gland releases GH in bursts.¹
3. Liver. GH tells your liver to make IGF-1. When IGF-1 rises, it tells the brain and the pituitary to slow down. This built-in brake stops GH and IGF-1 from rising without limit.¹

GH leaves your blood within minutes, so a single GH test depends on the exact moment the blood is taken. IGF-1 stays steady through the day. This is why we measure IGF-1, not GH.²

• Fat. GH helps your body break down fat for energy, including fat in the liver.¹
• Muscle. GH helps your body build muscle protein.¹
• Blood sugar. GH and IGF-1 pull in opposite directions. GH makes your body respond less to insulin for a while, and IGF-1 acts a little like insulin. This is why we look at your blood sugar before you start.¹
• A circle that feeds itself. Fat inside the belly lowers GH release, and low GH lets more fat build up inside the belly.¹

• You are getting older. GH release falls by about 14% for every ten years of adult life.³
• You carry extra fat around your belly. GH is lower in people with more belly fat, and it often comes back up after weight loss.¹
• You sleep too little. Most GH is released in deep sleep.¹

Standard medical guidelines do not treat the fall in GH with age as a disease. Physicians who focus on optimal hormone levels see it differently, and look at both your symptoms and your IGF-1 level.^(2,3)

Physicians who focus on optimal hormone levels look for these signs. We ask about them in a short questionnaire:

• Thinning hair
• Sagging cheeks
• Receding gums
• A soft, flabby belly
• Slack muscles
• Thin or dry skin
• Finding it hard to recover after exercise
• Feeling exhausted
• Wanting to stay away from people
• Feeling anxious or worried all the time

Many of these signs can also come from low sex hormones or other causes. This is why we always look at your blood test together with your symptoms, and why we check your other hormones too.

We don’t ask you to take our word for it. This is what research has found, and in which people:

• Body fat and muscle. In adults who truly lack GH because of a pituitary condition, GH treatment lowers body fat, especially around the middle, and raises lean mass. Studies agree on this.³
• Cholesterol. In the same group, GH treatment lowers LDL (“bad”) cholesterol, and helps most in people whose cholesterol was high to begin with.³
• Bones. In the same group, bone density rises, but this takes about 18 months to show.³
• Quality of life. In the same group, quality of life improves. It takes about 6 months to judge, and the benefit can last up to 10 years.³
• Belly fat. When 60 adults with belly fat and low GH used a peptide that helps the body release its own GH, fat inside the belly fell by 19% over 12 months. Triglycerides (a blood fat) fell by 20%, and CRP, a marker of inflammation, also fell. Body weight did not change.⁴
• Liver fat. In a trial in people living with HIV, the same kind of peptide lowered fat in the liver over 6 months.⁵
• Calm and focus. Physicians who focus on optimal hormone levels report that people with optimal GH often feel calmer, focus better and cope better with stress. This comes from doctors’ experience, not from trials.

Where research has not shown a benefit

• Clinical trials so far have not shown that raising GH helps with strength or quality of life in healthy older adults. In a one-year trial in 65 healthy adults aged 60 to 81, GH and IGF-1 rose to the levels of young adults. Lean mass rose, but strength, physical function and quality of life were no different from placebo.⁶
• Clinical trials so far have not shown that GH helps with strength in fit young adults. A review of studies in more than 300 young, fit people found that lean mass rose, but strength and exercise capacity did not.⁷
• These treatments are not weight-loss medicines. In the trials, body weight did not change.^(4,8)

We aim for the upper half of the normal range for your age and sex, not the level of a 20-year-old.

• Why we treat only below the middle. If your IGF-1 is already in the upper half of the range for your age, we do not give you these medicines, even if you have symptoms. Your level is already where we want it. Medicines that raise GH push IGF-1 up whatever your starting point, so starting from a good level makes it easy to go too high. Instead, we help you support your own GH naturally and check your other hormones.
• Why not higher. More is not better. Both high and low IGF-1 are linked with a higher death rate in adults.¹ When GH stays too high for a long time, the body needs more and more insulin, which can lead to diabetes.¹ In a large study of 15,809 adults treated with GH for about 5 years, people whose IGF-1 was in the upper half of the normal range did not get more cancer.⁹ Above the top of the range, there is no such information, so the top of the range is our ceiling.

Standard medical guidelines set our safety limits. Within those limits, we use the optimal-range approach to aim for the level where you benefit most. That is also why we keep checking your level.

• IGF-1. This is the test we use to decide whether to start and how to adjust. Results can differ a lot between laboratories and testing methods, so we use the same laboratory and the same method every time.² IGF-1 stays steady through the day, so you can have the test at any time and you do not need to fast.²
• Your Annual Panel. Everyone in our program has a yearly check of hormones, blood sugar, blood fats and more. GH lowers cortisol (a stress hormone) and thyroid hormone in some people, and can raise blood sugar, so we look at these results before you start.^(2,3)
• Stop biotin for 3 days before every blood test. Biotin, found in many hair and nail supplements, can make hormone results falsely high or low.

GH-releasing peptides are not one size fits all. Some people need special consideration before they start, because these medicines act on blood sugar, cortisol, thyroid hormone and growth, or because their pituitary gland may not respond. These people need closer care. Before you start, our doctor checks whether any of these apply to you:

• Diabetes, even when it is well controlled
• Cancer now or in the past, other than a basal cell or squamous cell skin cancer that was fully removed
• Symptoms that could point to cancer
• A pituitary condition, pituitary surgery, radiation to the head, or a recent head injury that needed a hospital stay
• A heart attack or stroke in the last 6 months, or heart failure
• Pregnancy, planning a pregnancy, or breastfeeding
• Low morning cortisol, or thyroid results outside the normal range
• Steroid tablets or injections taken regularly
• A serious illness or major surgery at the moment
• Other GH-boosting products you already use, such as other peptides, growth hormone injections or MK-677
• An IGF-1 level below or above the normal range for your age

For some of these, we adjust your plan or wait. For example, if you use a GH-boosting product from elsewhere, you stop it first, and we test your starting level at least 2 weeks later. Your IGF-1 takes about that long to return to your own level.¹⁰ For others, such as pituitary conditions, heart disease, diabetes or a level outside the normal range, the specialist who looks after you, or a hospital, is the right place to find the cause and treat it, so we refer you rather than start treatment ourselves.^(2,8)

Products sold elsewhere vary in quality, and your doctor cannot adjust treatment safely without knowing exactly what you use. Some treatments in our program are used off-label (outside a medicine’s official label) or are products that are not registered as medicines. Your doctor explains the benefits, the risks and your other choices, and asks you to sign a consent form before you start.

We do not give growth hormone itself. We use peptides (small proteins) that signal your own pituitary gland to release more of its own GH. This has three practical meanings:

• Your body’s brakes stay on. Your natural rhythm of release and your body’s brake system keep working. Injected growth hormone bypasses this system.¹⁰
• Your own production is not switched off. In a study of one of the peptides we use, the body’s own GH release went back to where it was within 2 weeks of stopping, not lower.¹⁰ This is an advantage, but it does not prove the treatment is safer overall, so we still check your blood.
• Your pituitary gland must be healthy. These medicines only work when the pituitary can respond. This is why we do not use them after pituitary disease or surgery.⁸

We start with the gentlest step. Everyone starts with the mildest peptide. You move up one step, at the start of your next cycle, only if your blood level is still below our target. You never use two GH peptides at the same time. Guidelines for growth hormone advise starting low and adjusting by IGF-1 to keep side effects down, and people respond very differently to the same dose.²

From our doctor One of our patients, who was not old, started a GH-releasing peptide at a full dose from the very beginning. Her body responded so well that within a few weeks her IGF-1 rose well above the top of the normal range. She had no symptoms, and she stopped the medicine. Younger people often respond more strongly, and nobody can tell in advance how strongly a person will respond. This is why we now start everyone on the gentlest step and move up only when a blood test shows it is needed.

Use and rest: the cycle. You use the medicine for 2–3 months, then rest for the same length of time. Physicians who focus on optimal hormone levels have found that the effect of medicines that boost GH release tends to fade after several weeks. Resting for the same length of time helps the next cycle work again. During the rest, your level returns to your own level within about 2 weeks.¹⁰

• One blood test in each cycle, while you are still using the medicine. Any time from 1 month after you start until before your rest begins. IGF-1 takes about a month to settle. It falls back within about 2 weeks of stopping,¹⁰ so a test during your rest would not show your level on treatment.
• If your level is below our target, you move up one step in your next cycle. If it is in the optimal range, you stay on the same step. If it is above the top of the range, we lower your step or stop, and check again. If your level is still high after you have stopped, it is not from the medicine, and we refer you to a hospital to find the cause.
• Before every new cycle, we ask again about diabetes, cancer, steroid medicines and pregnancy, because something new may have happened during your rest.
• Once a year, you have your Annual Panel.

1. Olarescu NC, Gunawardane K, et al. Normal Physiology of Growth Hormone in Normal Adults. In: Feingold KR, et al., editors. Endotext. MDText.com; updated 2025.
2. Yuen KCJ, Biller BMK, Radovick S, et al. American Association of Clinical Endocrinologists and American College of Endocrinology Guidelines for Management of Growth Hormone Deficiency in Adults and Patients Transitioning from Pediatric to Adult Care. Endocr Pract. 2019;25(11).
3. Feldt-Rasmussen U, Klose M. Adult Growth Hormone Deficiency – Clinical Management. In: Feingold KR, et al., editors. Endotext. MDText.com; updated 2022.
4. Makimura H, Feldpausch MN, Rope AM, et al. Metabolic Effects of a Growth Hormone-Releasing Factor in Obese Subjects with Reduced Growth Hormone Secretion: A Randomized Controlled Trial. J Clin Endocrinol Metab. 2012;97(12):4769–4779.
5. Stanley TL, Feldpausch MN, Oh J, et al. Effect of Tesamorelin on Liver Fat and Visceral Fat in HIV-Infected Patients With Abdominal Fat Accumulation: A Randomized Clinical Trial. JAMA. 2014;312(4):380–389.
6. Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an Oral Ghrelin Mimetic on Body Composition and Clinical Outcomes in Healthy Older Adults: A Randomized Trial. Ann Intern Med. 2008;149(9).
7. Liu H, Bravata DM, Olkin I, et al. Systematic Review: The Effects of Growth Hormone on Athletic Performance. Ann Intern Med. 2008;148(10).
8. Tesamorelin for injection, for subcutaneous use. US prescribing information. Revised 3/2025.
9. Johannsson G, Touraine P, Feldt-Rasmussen U, et al. Long-term Safety of Growth Hormone in Adults With Growth Hormone Deficiency: Overview of 15 809 GH-Treated Patients. J Clin Endocrinol Metab. 2022;107:1906–1919.
10. Stanley TL, Chen CY, Branch KL, Makimura H, Grinspoon SK. Effects of a Growth Hormone-Releasing Hormone Analog on Endogenous GH Pulsatility and Insulin Sensitivity in Healthy Men. J Clin Endocrinol Metab. 2011;96(1):150–158.