IGF-1 on Sermorelin: What the Number Means

Growth hormone is released in pulses — a few a day, the largest during deep sleep — and between pulses the blood level is close to nothing. A single growth-hormone blood test therefore tells you almost nothing: it depends on the minute the needle went in. IGF-1, by contrast, is produced steadily and has a long life in the blood, bound to carrier proteins, so its level on any given morning reflects growth-hormone exposure over the preceding days.

That is why IGF-1 is the standard marker for growth-hormone status in endocrinology — used to diagnose deficiency and excess, and to monitor treatment — and why it is the marker we use for sermorelin. The sleep page explains where the pulses come from; IGF-1 is how their sum is read.

IGF-1 is highest in adolescence, falls steeply through the twenties, and declines steadily thereafter, so that the reference range for a sixty-year-old is markedly lower than for a thirty-year-old. Laboratories report an age-adjusted range for exactly this reason, and a result must be read against the range for your age, not against a single "normal."

Two consequences. A man of fifty-five with an IGF-1 at the lower edge of his age range is, by definition, typical for his age — the decline is physiological, and a low-normal result is not a deficiency. And the same result in a thirty-year-old would be a reason to investigate. Which is the honest frame for sermorelin: it is prescribed for the age-related decline, not for a deficiency, and the cancer risk page explains why we aim to restore a value within the range for your age rather than push it above it.

It tells you the axis responded. Sermorelin works only if the pituitary can still answer a GHRH signal. A rise in IGF-1 after starting is evidence that it did — that the pituitary released more growth hormone and the liver made more IGF-1 in response. No rise, over an adequate period and with good adherence, suggests the axis is not responding, and is a reason to reconsider rather than to persist.

It confirms the tablet is being absorbed. The main page is candid that there are no published human absorption studies for the dissolving-tablet route. That makes IGF-1 the only objective evidence, in a given person, that the tablet is delivering sermorelin at all. It is the reason we monitor rather than assume.

It does not measure how you feel. IGF-1 is a marker of exposure, not of benefit. Some people report better sleep, recovery or body composition with a modest rise; others report the same with none; the correlation between the number and the experience is loose. A good result on paper with no change in how you feel is a reason to ask whether sermorelin is the right treatment, not a reason to chase a higher number.

It does not need to be high. More IGF-1 is not better. The relationship between IGF-1 and long-term health is U-shaped — both the lowest and the highest levels associate with worse outcomes in population studies — and the cancer risk page covers the upper end. The goal is the range for your age. A result above it is a reason to stop and discuss, not a success.

At baseline, before anything is prescribed — because a person whose IGF-1 is already at the upper end of their age range is not a sermorelin candidate, and because the baseline is what a later result is compared against. Then at review, once the effect has had time to appear, and periodically thereafter for as long as the treatment continues. IGF-1 is drawn in the morning, and it is worth telling us if you have been fasting hard, unwell or drinking heavily in the weeks before, because each of those moves it.