Abstract
Pregnancy is associated with a physiological GH excess, where maternal pituitary GH is suppressed by effect of placental GH on the hepatic receptor, increasing IGF-1 serum levels1. However, it is also described that estrogens and progesterone are responsible for reduction in IGF-1 by direct hepatic action through the inhibition of the JAK-STAT pathway that results in GH resistance, being more clear at the beginning of pregnancy.2 Acromegaly is a rare disorder in which GH axis is deregulated and IGF-1 is the most reliable biochemical marker for diagnosis and monitoring. It is know that secondary hypogonadism associated with these pathology decreases fertility rates. Nonetheless, improvement of acromegaly treatment and greater access to assisted reproductive technology increase pregnancy rates in this population. The follow-up of pregnant acromegalic women acquires relevance for the comorbidities of this association and depends on the adequate interpretation of the IGF-1 values. Then, due to changes in concentration and action of IGF-1 during pregnancy3, it is important that each laboratory establish their specific reference values. For that reason we analyzed serum samples from 80 healthy pregnant women living in the Metropolitan Area of Buenos Aires (AMBA): 22 were in the 1st trimester (1T), 29 in the 2nd (2T) and 29 in the 3rd (3T). All women were between 30 and 40 years old, had no endocrinopathies or metabolic diseases. Serum IGF-1 was measured by Immulite 2000 Siemens, and Prism8 GraphPad was used for statistical analysis, calculating ranges for each trimester defined as 2,5 and 97,5 percentiles. Ranges obtained were: 64,5-165,0 ng/ml, 78,9-201,0 ng/ml and 96,1-344,0 ng/ml for 1T, 2T and 3T, respectively. Significant differences were observed between 3T and the other trimesters (1T and 2T). We also compared these ranges with our reference values from healthy non-pregnant women in the same age, and found that 3T has significantly higher values of IGF-1 (55,8-188,4 ng/ml vs. 96,1-344,0 ng/ml respectively). In conclusion, IGF-1 levels during the first two trimesters of pregnancy remain within the normal range, and there is a significant increase during the third trimester. Given that IGF-1 plays an essential role during pregnancy, it is important to report ranges in healthy pregnant women to contribute in the follow-up of patients with acromegaly who get pregnant. Although our results are in agree with the available literature, it is necessary to increase the number of healthy pregnant women to establish reference values of IGF-1.
1Frankenne et al (1988). The physiology of growth hormones in pregnant women and partial characterization of the placental GH variant. Journal of Clinical Endocrinology and Metabolism 66:1171-1180
2Leung et al (2004). Estrogen regulation of growth hormone action. Endocrine Reviews 25:693-72
3Muhammad et al (2017). Pregnancy and acromegaly. Pituitary 20:179-184
Evaluation of maternal thyroid function during pregnancy: the importance of using gestational age-specific reference intervals
