Insulin-like Growth Factor 1 (IGF-1) is a naturally occurring hormone structurally similar to insulin, playing a significant role in the body’s growth and development processes. This hormone is primarily produced by the liver, with its synthesis stimulated by Growth Hormone (GH), which is released from the pituitary gland. IGF-1 then circulates throughout the bloodstream, influencing nearly every cell and tissue to promote growth and cellular function.
IGF-1 Levels Across the Lifespan
IGF-1 levels vary throughout an individual’s life, reflecting different stages of growth and development. They are typically expressed in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L). While ranges can differ slightly between laboratories, the overall patterns remain consistent.
In infancy and early childhood, IGF-1 levels are low, gradually increasing with age. For children aged 1-5 years, levels may range from 1.6 to 32.9 nmol/L, depending on sex. In later childhood (9-11 years), these levels rise further, potentially reaching 3.0 to 71.9 nmol/L.
The most dramatic surge in IGF-1 occurs during puberty, coinciding with the adolescent growth spurt. Between 12 and 20 years of age, IGF-1 concentrations peak, driving rapid bone and tissue growth. Individuals aged 12-15 years may have ranges from 6.4 to 78.1 nmol/L, while 16-20 year olds show 14.3 to 66.9 nmol/L.
After the pubertal peak, IGF-1 levels plateau in early adulthood before gradually declining throughout middle age. For adults aged 25-39 years, ranges are typically 10.7 to 37.1 nmol/L, and for those aged 40-54 years, 8.1 to 31.0 nmol/L. This decline reflects the body’s decreased growth demands and metabolic changes.
In older adulthood, IGF-1 levels continue to decline, reaching their lowest concentrations. Individuals over 55 years may have levels in the range of 2.0 to 32.2 nmol/L. Consulting specific laboratory reference ranges is recommended for accurate interpretation of individual results.
Causes of Abnormal IGF-1 Levels
When IGF-1 levels fall outside the expected range for an individual’s age, it can signal underlying health conditions. Both unusually low and unusually high concentrations warrant medical investigation to determine the cause.
Low IGF-1 levels can stem from several factors, most commonly insufficient Growth Hormone (GH) production. Growth Hormone Deficiency (GHD), often due to pituitary or hypothalamic issues, reduces IGF-1 synthesis. Hypopituitarism, where the pituitary produces too little GH, also diminishes IGF-1. Liver disease can impair the liver’s ability to produce IGF-1, even with adequate GH. Severe malnutrition or protein deficiency can also reduce IGF-1 levels.
Conversely, elevated IGF-1 levels are often associated with Growth Hormone overproduction. Pituitary tumors that produce excessive GH are a common cause. In children, this overproduction leads to gigantism. In adults, it manifests as acromegaly, causing enlargement of hands, feet, and facial features. Pregnancy can also lead to temporarily higher IGF-1 levels due to hormonal changes.
The Process of IGF-1 Evaluation
Evaluating IGF-1 levels involves a straightforward blood test, a common initial step in assessing growth-related disorders or suspected hormone imbalances. IGF-1 is frequently tested because of its stable presence in the bloodstream. Unlike GH, which is released in pulsatile bursts and fluctuates significantly, IGF-1 levels remain constant, providing a reliable indicator of average GH secretion.
A healthcare provider collects a blood sample; fasting may sometimes be required. An abnormal IGF-1 result serves as a screening indicator, suggesting a hormone imbalance rather than providing a definitive diagnosis. Such a result often prompts further diagnostic steps to pinpoint the underlying cause.
These additional investigations may include dynamic function tests, such as GH stimulation tests for deficiency or GH suppression tests for excess GH production. Imaging studies, like an MRI of the pituitary gland, are also performed to check for tumors or structural abnormalities. This comprehensive evaluation helps clinicians determine the appropriate course of action based on the confirmed diagnosis.