Pregnancy‐induced changes in insulin‐like growth factor I (IGF‐I), insulin‐like growth factor binding protein 3 (IGFBP‐3), and acid‐labile subunit (ALS) in patients with growth hormone (GH) deficiency and excess

Abstract Background. Under most circumstances with altered growth hormone (GH) secretion, the changes of insulin‐like growth factor I (IGF‐I), insulin‐like growth factor binding protein 3 (IGFBP‐3), and acid‐labile subunit (ALS) are in parallel. The aim of the present study was to compare the effects of pregnancy in a hypopituitary patient with those of pregnancy in an acromegalic patient on IGF‐I, IGFBP‐3, and ALS. Methods and results. IGF‐I and ALS were low before pregnancy in the hypopituitary patient under glucocorticoid and thyroxine treatment. Gonadotropin treatment allowed her to become pregnant; IGF‐I and ALS levels rose in the second half of pregnancy and fell again after delivery. IGF‐I concentrations were elevated in the patient with persistent acromegaly before and dropped into the normal range during the first half of pregnancy. In the second half of pregnancy and following delivery, IGF‐I levels increased again. IGFBP‐3 levels (as assessed by immunoblot analysis as well as by 125 I‐IGF II ligand blotting) decreased markedly during pregnancy in both patients, suggesting that the placenta rather than pituitary GH regulates IGFBP‐3 proteolysis in human pregnancy. The increase of IGF‐I (and ALS) during the second half of pregnancy in the individual with pituitary GH deficiency may be attributed to placental GH. The fall of IGF‐I (and ALS) into the normal range in the acromegalic patient during the first trimester of pregnancy may be related to decreased production or decreased half‐life of these proteins. Conclusion. Our data suggest that measures to continuously replace GH or to suppress GH secretion during pregnancy in patients with GH deficiency or excess, respectively, may not be warranted.