Decreased IGF-1 concentration during the first trimester of pregnancy in women with normal somatotroph function.

Abstract

A decrease of insulin-like growth factor-I levels (IGF-I) has been reported during the first trimester of pregnancy in women with acromegaly before the secretion of placental growth hormone (GH) progressively increases IGF-1 concentration. To evaluate variations of concentrations of IGF-1, insulin-like growth factor (IGF)-binding protein-3 (IGF-BP3) and GH during the first trimester of pregnancy in women with normal somatotroph function. Sixteen women (median age 31years) with as who were followed for benign thyroid disorders (n=15) or prolactin-secreting microadenoma (n=1) were evaluated before and in the first trimester of pregnancy. Serum concentrations of GH, IGF-1, IGF-BP3, TSH and estradiol (E2) were measured before and in the first trimester (5.4±2.2weeks of gestation). Before pregnancy, somatotroph and thyroid functions (median TSH 1.2mU/L) were normal in all women. At the first trimester IGF-1 levels decreased significantly (before=210ng/mL, first trimester=145ng/mL, p<0.001) with no significant change in GH (before=1.5ng/mL, first trimester=0.84ng/mL) or IGF-BP3 levels (before=2.3ng/mL, first trimester=2.2ng/mL), while estradiol levels increased significantly (before=46.5pg/100mL, first trimester=448.5pg/100mL, p<0.001). In women with normal somatotroph function, IGF-1 levels decrease in the first trimester of pregnancy without changes in GH or IGF-BP3 levels. These results confirm liver resistance to GH as a consequence of the physiological increase of estrogens during the first trimester.