Growth hormone (GH), also called somatotropin, is produced by the pituitary gland. GH stimulates growth in children, maintains tissue regeneration and body composition in adults, and affects metabolism by increasing insulin resistance and raising blood glucose. GH acts mainly through IGF-1 (insulin-like growth factor 1) produced by the liver. GH is released in pulses, especially during sleep — making single measurements unreliable. IGF-1 is the more reliable test because it reflects average GH activity. For diabetes: GH excess (acromegaly) commonly causes diabetes — 25-50% of adults with acromegaly develop diabetes; GH deficiency rare in adults except after pituitary surgery/radiation. Acromegaly is a disorder of excess growth hormone in adults, almost always from a benign pituitary tumor (adenoma). Effects on diabetes: GH increases insulin resistance, increases hepatic glucose production, may damage pancreatic beta cells. Other acromegaly features: gradual enlargement of hands, feet, jaw, brow (over years); coarsening facial features; joint pain; headaches; sleep apnea (often severe); vision changes; excessive sweating; cardiovascular issues. Rare disease (1 in 100,000+) but underdiagnosed because changes occur slowly. Testing methods: random GH usually NOT useful (pulsatile); IGF-1 most reliable measure (reflects average GH activity); oral glucose tolerance test with GH measurement is gold standard (healthy adults suppress GH to under 1 ng/mL after glucose load; acromegaly fails to suppress); MRI pituitary if biochemical tests confirm. For most adults with diabetes, growth hormone testing is not part of standard evaluation; ordered when acromegaly suspected. Treatment of acromegaly (surgery, medications, radiation) often reverses or improves diabetes.
Growth Hormone and Diabetes
- GH increases insulin resistance.
- GH stimulates hepatic glucose production.
- GH may damage pancreatic beta cells with chronic excess.
- Acromegaly (GH excess): 25-50% develop diabetes.
- “Diabetogenic” effect explains acromegaly-diabetes connection.
- Treating acromegaly often reverses or improves diabetes.
- GH deficiency rare in adults; usually after pituitary surgery/radiation.
- Adult GH deficiency can also affect body composition and metabolism.
Acromegaly Features (Develop Gradually Over Years)
- Enlargement of hands, feet, jaw, brow.
- Changes in shoe size, ring size, hat size.
- Coarsening facial features.
- Prognathism (jutting jaw).
- Wide tooth spaces.
- Deep voice (vocal cord thickening).
- Joint pain and arthritis.
- Headaches.
- Vision changes (tumor pressing on optic nerve).
- Sleep apnea (often severe).
- Excessive sweating (hyperhidrosis).
- Skin tags.
- Cardiovascular issues — hypertension, heart enlargement.
- New diabetes onset.
- Carpal tunnel syndrome.
- Erectile dysfunction in men.
Testing Methods for GH/IGF-1
| Test | Purpose | Normal Result |
|---|---|---|
| Random GH | Usually NOT useful (pulsatile) | Highly variable |
| IGF-1 | Best initial test for acromegaly | Age-adjusted; varies |
| OGTT with GH measurement | Gold standard for acromegaly | GH suppresses to under 1 ng/mL after glucose |
| Insulin tolerance test | GH deficiency evaluation | GH should rise after insulin-induced hypoglycemia |
| GHRH stimulation | GH deficiency | Specialized; less common |
| MRI pituitary | Image pituitary tumor | Normal pituitary; or detect adenoma |
IGF-1 Reference Ranges (by age)
| Age | IGF-1 Range (ng/mL) |
|---|---|
| Adult 20-30 | 116-358 |
| Adult 30-40 | 109-284 |
| Adult 40-50 | 87-238 |
| Adult 50-60 | 74-196 |
| Adult 60-70 | 57-164 |
| Adult over 70 | 49-127 |
| Children/adolescents | Higher; varies by puberty stage |
Acromegaly Treatment Options
- Surgery: transsphenoidal resection of pituitary tumor; first-line for most cases.
- Somatostatin analogs: octreotide, lanreotide — suppress GH production.
- GH receptor antagonist: pegvisomant — blocks GH action.
- Dopamine agonists: cabergoline — modest benefit for some.
- Radiation: stereotactic radiosurgery; for residual disease.
- Combination therapy: often needed.
- Treatment goal: normalize IGF-1 and reduce tumor size.
- Treatment often reverses or improves diabetes.
- Long-term follow-up at endocrine center recommended.
When to Suspect Acromegaly in Diabetes
- Gradual changes in facial appearance (review old photos).
- Changes in shoe, ring, hat size over years.
- Severe sleep apnea.
- New diabetes with unusual features.
- Severe joint pain.
- Persistent headaches with vision changes.
- Excessive sweating.
- Carpal tunnel syndrome (especially bilateral).
- Family history of pituitary tumors.
- Skin tags and oily skin.
- If suggestive, order IGF-1 testing as initial screen.
GH Deficiency in Adults
- Rare — usually after pituitary surgery, radiation, or trauma.
- Symptoms: fatigue, decreased exercise tolerance, increased body fat (central), decreased muscle.
- Lower bone density.
- Mood changes.
- Affects insulin sensitivity (effects more variable).
- Treatment: GH replacement (somatropin) injection.
- Treatment specialized at endocrine centers.
- Not routinely tested for diabetes.
The Bottom Line
Growth hormone (GH), also called somatotropin, is produced by the pituitary gland. GH stimulates growth in children, maintains tissue regeneration and body composition in adults, and affects metabolism by increasing insulin resistance and raising blood glucose. GH acts mainly through IGF-1 (insulin-like growth factor 1) produced by the liver. GH is released in pulses, especially during sleep — making single measurements unreliable. IGF-1 is the more reliable test because it reflects average GH activity. For diabetes: GH excess (acromegaly) commonly causes diabetes — 25-50% of adults with acromegaly develop diabetes; GH deficiency rare in adults except after pituitary surgery/radiation. Acromegaly is a disorder of excess growth hormone in adults, almost always from a benign pituitary tumor (adenoma). Mechanism: GH increases insulin resistance, increases hepatic glucose production, may damage pancreatic beta cells. Acromegaly features (develop gradually over years): enlargement of hands, feet, jaw, brow; changes in shoe/ring/hat size; coarsening facial features; prognathism; deep voice; joint pain; headaches; vision changes; severe sleep apnea; excessive sweating; skin tags; cardiovascular issues; new diabetes onset; carpal tunnel syndrome. Rare disease (1 in 100,000+) but underdiagnosed because changes occur slowly — look at old photos to track gradual changes. Testing methods: random GH usually NOT useful (pulsatile); IGF-1 most reliable measure (age-adjusted ranges); oral glucose tolerance test with GH measurement is gold standard (healthy adults suppress GH to under 1 ng/mL after glucose load; acromegaly fails to suppress); MRI pituitary if biochemical tests confirm. Acromegaly treatment options: surgery (transsphenoidal resection — first-line), somatostatin analogs (octreotide, lanreotide), GH receptor antagonist (pegvisomant), dopamine agonists (cabergoline), radiation. Treatment often reverses or improves diabetes. When to suspect acromegaly in diabetes: gradual facial changes (review old photos), changes in shoe/ring/hat size over years, severe sleep apnea, severe joint pain, persistent headaches with vision changes, excessive sweating, carpal tunnel syndrome, skin tags, family history of pituitary tumors. If suggestive, order IGF-1 as initial screen. GH deficiency in adults is rare (usually after pituitary surgery/radiation); not routinely tested for diabetes. For most adults with type 2 diabetes, growth hormone testing is not part of standard evaluation; reserved for adults with suggestive features of acromegaly. Diagnosing acromegaly leads to specialized treatment that often resolves the associated diabetes. See our broader diabetes detection guide for context.
