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Ask Nurse Lynn: Determining Growth Hormone Dose

Question

Male, 9 months old, UPD subtype

Hi nurse Lynn.
My son’s IGF-1 level is at 70ng/ml. The endocrinologist says it is the normal range. I would like to know what is the higher range he is supposed to be in? I can’t find the information only and I need it for my next appointment to argue a little with his doctor!

Nurse Lynn’s Response:

When doctors care for a baby with PWS on growth hormone, they do not look at just one number. They watch how quickly your child is growing taller, changes in muscle and body fat, sleep breathing, overall health, and blood tests like IGF-1 and IGFBP-3. IGF-1 shows how the body is responding to growth hormone, and the normal range depends on age. Babies naturally have lower IGF-1 levels than older children. For a baby around 9 months old, many labs show a range of about 20–150 ng/mL depending on the specific laboratory assay used, so a level of 70 ng/mL is usually within the normal range. Some specialists also look at the IGF-1 to IGFBP-3 ratio, which may give a more complete picture of growth hormone effect. In PWS, doctors usually do not aim for the highest IGF-1 level. Instead, they try to keep IGF-1 in the normal range, often the middle to upper part, while making sure sleep studies are safe and there are no side effects like swelling, joint discomfort, or breathing changes. The goal is healthy growth and strength, not just a higher lab number.

As always, Ask Nurse Lynn is for education and support and does not replace medical care from your child’s physician. Physicians consider many factors when prescribing and adjusting growth hormone in PWS. If you have concerns about your child’s IGF-1 level or dosing, it is always appropriate to bring your questions to your endocrinology team so decisions can be made together.

Resource Links:

ECHO 4 PWS: Endocrinology 101

2025 United in Hope PWS Conference: Endocrinology Issues for Children with PWS

Growth-Hormone-booklet-third-Edition_FINAL.pdf

The Importance of Growth Hormone Therapy for PWS

FPWRC 2009 Conference Dr Miller PWS Growth Hormone Dosing Guidelines

Please note that we are temporarily pausing submissions for our Ask Nurse Lynn column from July 12 – August 24, 2026.

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