Enter your information to understand your IGF-1 levels.

The History of IGF-1

The story of IGF-1 began in 1957, when endocrinologist William Daughaday proposed that growth hormone doesn't act directly on bone and cartilage tissue, but instead stimulates the liver to produce a separate, intermediary substance he termed "sulfation factor," later renamed somatomedin as researchers gradually came to better understand its true biological function. Swiss researchers Ernst Rinderknecht and René Humbel finally isolated and chemically sequenced this substance in 1978, discovering it shared a strikingly similar molecular structure to insulin itself, a finding that led them to rename it insulin-like growth factor, or IGF-1, the name still used universally in medicine today. This discovery fundamentally and permanently reshaped scientific understanding of the entire growth hormone system, revealing that growth hormone's effects throughout the body are largely mediated indirectly through this crucial intermediate hormone rather than through any direct action on target tissue itself.

What IGF-1 Actually Is

IGF-1 is a hormone produced predominantly by the liver in direct response to growth hormone stimulation, then released into the bloodstream, where it promotes the growth of bone, cartilage, and muscle tissue throughout childhood and adolescence, while continuing to support important anabolic tissue-repair processes throughout adult life as well. Because IGF-1 levels remain considerably more stable throughout the day than growth hormone itself, which fluctuates dramatically in short pulses, doctors actually prefer testing IGF-1 as a far more practical and genuinely reliable window into overall growth hormone activity measured over time. Abnormally low IGF-1 levels can indicate growth hormone deficiency or malnutrition, while genuinely elevated levels often point toward acromegaly, a rare condition caused by excessive growth hormone production, most commonly caused by a benign pituitary gland tumor located at the base of the brain.

How IGF-1 Is Measured

IGF-1 is measured from a standard blood sample using automated immunoassay platforms, in which specific antibodies bind directly to IGF-1 molecules, generating a measurable signal proportional to its actual concentration circulating in the bloodstream at that given moment. Because IGF-1 normally circulates tightly bound to specialized carrier proteins that can otherwise interfere with accurate antibody binding, modern assays include a careful extraction step designed to separate IGF-1 from those binding proteins before testing, meaningfully improving overall measurement accuracy and consistency across different laboratories and testing platforms nationwide. Reference ranges for IGF-1 vary considerably by age, since levels naturally peak during adolescence and gradually decline throughout normal, healthy adult aging.

Scientists Behind the Science

William Daughaday's original 1957 somatomedin hypothesis provided the essential conceptual breakthrough that eventually led researchers toward IGF-1's later discovery, correctly recognizing decades earlier that growth hormone's effects were mediated indirectly rather than acting directly on target tissue. Ernst Rinderknecht and René Humbel then completed that scientific journey in 1978, precisely identifying IGF-1's actual molecular structure and definitively confirming its remarkable, previously unsuspected similarity to insulin. Together, their combined discoveries, separated by more than two decades of dedicated endocrine research, transformed a purely theoretical concept into one of the most clinically important hormones used today for evaluating growth disorders and pituitary gland function.