Long-term monitoring of insulin-like growth factor I in adult growth hormone deficiency: a critical appraisal.
Serum insulin-like growth factor I (IGF-I) levels predominantly reflect the hepatic effect of growth hormone (GH). Compared with serum GH levels, which reflect pulsatile GH secretion, serum IGF-I levels exhibit no major diurnal variation and thus provide a better estimate of integrated GH secretion in an individual patient. Measurement of serum IGF-I levels allows reliable identification of states of GH excess. In contrast, in a large proportion of adults with severe GH deficiency, serum IGF-I levels are within the normal range. Serum IGF-I levels increase markedly in response to GH administration and are often used as a surrogate variable for overall responsiveness to such treatment. Current data, however, suggest a poor relationship between changes in or levels of IGF-I and efficacy variables such as body composition, muscle function and well-being. The use of serum IGF-I as a guide during dose titration in the initial phase of treatment and during long-term monitoring of GH replacement therapy in adults, and its use as a safety marker or predictor of future morbidity and mortality are discussed here.
Gibney
James
J
Department of Endocrinology, St. Vincent's University Hospital, Dublin, Ireland.
Johannsson
Gudmundur
G
D000172:Acromegaly / Q000150:complications; D000328:Adult; D017668:Age of Onset; D002352:Carrier Proteins / Q000097:blood; D005260:Female; D006023:Glycoproteins / Q000097:blood; D019382:Human Growth Hormone / Q000172:deficiency* / Q000627:therapeutic use*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged
D002352:Carrier Proteins; D006023:Glycoproteins; D018972:Insulin-Like Growth Factor Binding Protein 3; C075944:insulin-like growth factor binding protein, acid labile subunit; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I