Normal Reference Range of Serum Insulin-Like Growth Factor (IGF)-I in Healthy Thai Adults
Wanee Plengpanich MSc*, Jintara Mangkala MD*, Patinut Buranasukajorn MD*, Kanjana Boonruang BSc*, Sarat Sunthornyothin MD*, Sompongse Suwanwalaikorn MD*, Weerapan Khovidhunkit MD, PhD*, Vitaya Sridama MD*, Thiti Snabboon MD*
Affiliation : * Division of Endocrine and Metabolism, Department of Internal Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok
Background : Serum insulin-like growth factor (IGF)-I level is growth hormone (GH) dependent and reflects
GH secretion. Analysis of IGF-I is a component in the diagnosis of GH-related disorders and is going to be of
interest in determining the risk of many disorders such as cancer or atherosclerosis. The diagnosis value of
IGF-I is dependent on the establishment of an accurate reference ranges, which can be affected by parameters
such as age, gender, ethnicity, medications, chronic illness, or assay methodologies.
Objective : To determine reference ranges of IGF-I for healthy Thai adults.
Material and Method: Eight hundred sixteen healthy Thai adults aged between 21-70 years were recruited in
the present study. Serum IGF-I was measured by using immunochemiluminescent (ICMA; Roche, USA). Subjects
were recorded by their age and gender groups. Data were presented in mean and + 2 standard deviation (SD).
Correlation analysis between serum IGF-I and physical parameters including sex, age, weight, height, and
body mass index (BMI) was also made.
Results : The present study demonstrated normal reference range of serum IGF-I by using mean + 2SD value.
The well-known age dependency of serum IGF-I levels was also revealed. Levels decreased with increasing
age in both genders. The mean value of serum IGF-I was slightly higher in women at the age of 30-40 years
compared with men in the same age group, but not statistically insignificant. In addition, serum IGF-I was
found to correlate directly with the height and negatively with BMI. However, age-adjusted IGF-I level did not
show correlation with these physical parameters.
Conclusion : This reference range will be beneficial for using IGF-I assay as a tool in the diagnosis of GH
function abnormalities in Thai subjects.
Keywords : IGF-I, Growth Hormone
