Growth Hormone Test · Blood

If someone asked you to name a hormone linked to heart disease risk, you would probably say insulin or cortisol. Growth hormone would not make the list. But a large Swedish study that followed over 4,300 adults for more than 16 years found that people with the highest fasting growth hormone levels had nearly triple the risk of dying from cardiovascular disease compared to those with the lowest levels. That association held up even after accounting for cholesterol, blood pressure, blood sugar, and every other standard risk factor.

GH (growth hormone, also called somatotropin) is a 191 amino acid protein made by somatotroph cells in the anterior pituitary gland, a pea-sized structure at the base of the brain. Your body releases GH in pulses, with the largest bursts during deep sleep. That pulsatile nature makes a single random GH reading tricky to interpret, which is why this test works best when drawn fasting, under consistent conditions, and ideally tracked alongside IGF-1 (insulin-like growth factor 1), a separate blood marker that reflects your overall GH activity more steadily.

How Growth Hormone Works

When GH enters your bloodstream, it binds to receptors on cells throughout the body. In the liver, this triggers the production of IGF-1, which carries out many of GH's downstream effects: stimulating bone and cartilage growth, breaking down stored fat for energy, building and maintaining muscle, and supporting tissue repair. Roughly 75% of the IGF-1 circulating in your blood comes from the liver in response to GH.

Your brain keeps GH in check through two opposing signals from the hypothalamus, a brain region that coordinates hormone release: GHRH (growth hormone releasing hormone) pushes somatotroph cells to secrete more GH, while somatostatin tells them to stop. A stomach hormone called ghrelin also stimulates GH release, which is one reason GH levels rise when you are fasting. When IGF-1 levels get high enough, IGF-1 feeds back to the hypothalamus and increases somatostatin, dialing GH secretion back down. A study in six healthy men showed that IGF-1 infusions suppressed GH secretion by about 85%, mainly by shrinking the size and frequency of GH pulses.

Heart Disease and Death Risk

The strongest evidence linking fasting GH to cardiovascular outcomes comes from two prospective cohort studies that measured fasting GH using high-sensitivity assays and then tracked participants for years.

Sources: Malmö Diet and Cancer Study (Hallengren et al.); REGARDS Study (Wettersten et al.)

In the Malmö study, the connection between higher fasting GH and cardiovascular death remained strong even after adjusting for insulin, HbA1c, kidney function, a heart failure marker called NT-proBNP, and body fat. Adding fasting GH to a standard risk factor model significantly improved the ability to correctly classify who would die from cardiovascular causes and who would not.

What this means for you: if your fasting GH is consistently in the upper range, it may signal cardiovascular risk that your standard lipid panel and metabolic labs are not capturing. This does not mean high GH causes heart disease directly. It may instead reflect a state where your body is producing more GH because tissues are not responding to it effectively, similar to how high insulin can signal insulin resistance rather than insulin abundance.

When Too Little GH Is Also a Problem

This is not a simple "lower is better" marker. Adults with genuine growth hormone deficiency (GHD), usually from pituitary damage caused by tumors, surgery, or radiation, also face elevated cardiovascular risk. A study of 1,411 adults with underactive pituitary glands who were not receiving GH replacement found significantly increased rates of death, heart attacks, strokes, and cancer compared to the general population.

In chronic heart failure, GH deficiency is surprisingly common, present in roughly 30% of patients in one study of 130 people with heart failure. Those with GHD had worse exercise capacity, more advanced heart remodeling, and higher death rates. When 64 heart failure patients with confirmed GHD were randomized to either GH replacement or placebo for one year, those receiving GH improved their peak exercise capacity from 12.8 to 15.5 mL/kg/min and showed better right-heart function.

The pattern, then, is context-dependent: both chronically elevated fasting GH in the general population and genuine GH deficiency in people with pituitary disease are associated with worse cardiovascular outcomes. Think of GH less as a "good number or bad number" marker and more as a window into whether your pituitary-metabolic axis is functioning in its healthy range. The risk sits at both extremes.

Cancer Associations

The GH-IGF-1 signaling pathway can promote cell growth and survival, which raises a natural question about cancer risk. The largest study to address this, the European SAGhE cohort, tracked 23,984 people who received recombinant GH treatment during childhood. In those treated for isolated GH deficiency or short stature without other major disease, there was no general increase in cancer risk. However, among patients who had already been treated for a prior cancer, cancer death risk increased significantly with higher daily GH doses.

A separate analysis of the same cohort, expanded to 24,232 patients with over 400,000 patient-years of follow-up, confirmed that all-cause mortality was not elevated in low-risk patients (those with isolated GH deficiency or short stature). Deaths from circulatory and blood-related diseases, though, were increased across all risk groups, reinforcing the cardiovascular signal.

What this means for you: if you have a personal history of cancer, understanding your GH and IGF-1 levels carries additional weight. Discuss any supplementation or optimization strategies with an oncologist or endocrinologist who understands this nuance.

IGF-1: The Companion Marker

Because GH is released in pulses and varies enormously from hour to hour, IGF-1 is the more stable blood marker that reflects your average GH activity over days to weeks. A single random GH measurement can be nearly undetectable in a perfectly healthy person simply because the blood was drawn between pulses. IGF-1 does not have this problem. It changes slowly and gives a much more reliable snapshot of your GH axis.

A large study from the EPIC-Heidelberg cohort, tracking over 7,400 participants for a median of 17.5 years, found that IGF-1 (a related but different measurement from GH itself) showed a U-shaped relationship with death risk. Both the lowest and highest fifths of IGF-1 were associated with higher rates of cancer death, cardiovascular death, and death from any cause compared to the middle range. Some of the risk at the low end was partially explained by liver dysfunction, which can lower IGF-1 independently of GH status. This U-shaped pattern is consistent with the idea that both deficiency and excess in the GH-IGF-1 system carry risks.

Reference Ranges

Interpreting a single GH value is harder than for almost any other blood test. GH is pulsatile, and different lab instruments can give results that differ by two to six times for the same blood sample. Results also vary by sex, age, and body weight. The ranges below come from a Russian multicenter study of 758 healthy adults measured on a single platform (Beckman DxI 800). They are illustrative orientation, not universal targets. Your lab will likely report different numbers.

Notice how wide these ranges are, and how low the medians sit. Most random or fasting blood draws in healthy adults will show GH below 1 ng/mL. Women tend to have higher basal and random GH than men. The cardiovascular outcome studies (Malmö, REGARDS) used fasting high-sensitivity GH assays to detect values that standard assays might report as undetectable. If your lab uses a conventional GH assay, very low readings are expected and do not necessarily indicate deficiency.

There is no published "optimal" fasting GH range for preventive health or longevity. The Endocrine Society guideline for adult GH deficiency recommends titrating GH replacement therapy to keep IGF-1 within the age-adjusted normal range but does not define a target GH level itself. For the preventive-minded reader, the most useful approach is to compare your own results within the same lab over time, rather than trying to hit a specific number.

When Results Can Be Misleading

GH has among the highest biological variability of any commonly measured hormone. A single reading can be distorted by factors that have nothing to do with your underlying GH status.

• Body weight: Higher BMI suppresses GH secretion. If you carry significant excess weight, your GH may look artificially low, potentially mimicking GH deficiency on a stimulation test. Revised, lower diagnostic cutpoints have been proposed for overweight and obese adults to avoid this misclassification.
• Time of day and sleep: GH peaks during deep sleep and varies throughout the day. A morning fasting draw will give different results than an afternoon draw.
• Recent vigorous exercise: Intense physical activity above a high-intensity threshold (roughly where breathing becomes hard enough that you cannot hold a conversation) triggers a GH surge that can persist for hours. If you exercised hard the morning of your blood draw, your result may be artificially elevated.
• Recent food intake or glucose loading: Eating, especially carbohydrates, acutely suppresses GH. A non-fasting sample will typically show lower GH than a fasting one. This is also the basis of the oral glucose tolerance test used to diagnose acromegaly (GH excess).
• L-dopa (levodopa): Used for Parkinson's disease, this medication causes a pronounced GH rise within about two hours that can persist for hours. If you take L-dopa, your GH reading may be substantially elevated without any pituitary abnormality.
• Adrenergic medications: Beta-blockers like propranolol can increase GH, while beta-stimulants can suppress it. Alpha-adrenergic agents have the opposite pattern. These shifts do not indicate real GH disease.

Acute illness, major surgery, and traumatic brain injury can also disrupt the GH axis for weeks to months. Avoid testing during or shortly after any of these events unless you are specifically evaluating pituitary damage.

Tracking Your Trend

Given the extreme variability of a single GH measurement, tracking your fasting GH over time is far more valuable than reacting to any one number. A consistent pattern across two or three fasting morning draws, ideally at the same lab, gives you a much clearer picture of your actual GH status than any individual result.

If you are testing GH for the first time as part of a preventive health screen, pair it with IGF-1 on the same draw. IGF-1 has a within-person variability of about 8% in healthy individuals, compared to GH's much wider swings. If your GH looks unexpectedly high or low but your IGF-1 is solidly in the normal range for your age, the GH reading was likely influenced by timing or a transient confounder. If both GH and IGF-1 are abnormal in the same direction, that pattern is more meaningful and worth investigating.

A reasonable cadence: get a baseline fasting GH and IGF-1 together. If both are normal, recheck annually or when symptoms change. If results are borderline or discordant, retest in 4 to 8 weeks under identical fasting, morning conditions before pursuing further workup.

What to Do With Your Result

If your fasting GH is persistently elevated (upper range on repeated draws) with normal or high IGF-1, the next step is an endocrinology evaluation to rule out early acromegaly (GH-producing pituitary tumor). This typically involves an oral glucose tolerance test to see whether GH suppresses normally after a glucose load, plus pituitary MRI if GH fails to suppress.

If your fasting GH is very low and your IGF-1 is also below the age-adjusted range, especially if you have symptoms like unexplained fatigue, increased belly fat, reduced exercise capacity, or loss of muscle mass, ask about formal stimulation testing. The insulin tolerance test and glucagon stimulation test are the standard tools for confirming adult GH deficiency. An endocrinologist can determine which test is appropriate.

If your fasting GH is elevated but your IGF-1 is normal, the most likely explanation is a confounder (body composition, timing, medication, stress) rather than pituitary disease. Retest under controlled conditions before escalating. The cardiovascular risk data from population cohorts applies to fasting GH, so pairing your result with other cardiovascular risk markers (ApoB, hs-CRP, HbA1c, blood pressure) puts the GH finding in proper context.