Placental Growth Hormone Is Not Suppressed by Oral Glucose Loading in Normal Human Pregnancy

Abstract

Placental growth hormone (PGH) progressively replaces pituitary growth hormone in the maternal circulation from mid-gestation onwards in human pregnancy. Our previous investigations have shown that placental growth hormone concentrations correlate well with foetal growth. Despite the apparent correlation between PGH and birthweight, the physiology of its secretion during pregnancy has not been well defined. We investigated the response of maternal serum PGH to oral glucose loading in pregnant women (n = 24) who demonstrated normal glucose tolerance at a mean gestation of 29 weeks. Mean (SEM) fasting PGH concentrations were high (36.9 [6.4] ng/ml). No suppression of PGH was noted at one, two or three hours after a 75 g oral glucose load. Similarly, no changes were noted in growth hormone binding protein or in calculated free PGH over the course of the glucose tolerance test. As expected, insulin concentrations rose sixfold and insulin like growth factor binding protein 1 concentrations fell by 20 % with glucose loading. Correlation analysis showed maternal weight, BMI, fasting serum glucose serum insulin to be significantly correlated with the babies' birthweight. Our results support the proposition that PGH concentrations in maternal serum are not suppressed by oral glucose loading in non-diabetic mothers.

Growth hormone binding protein and maternal body mass index in relation to placental growth hormone and insulin requirements during pregnancy in type 1 diabetic women

“…It is therefore not apparent, that PGH in itself is responsible for the development of insulin resistance during pregnancy. Conversely, oral glucose loads have been reported to decrease PGH levels in gestational diabetes, but this was not confirmed in non-diabetic women [30,31]. Studies in pregnant type 2 diabetics or gestational diabetes would be relevant in order to explore the relationship between increased BMI, insulin levels and the growth hormone axis.…”

Aspects of placental growth hormone physiology

“…Finally, PGH levels were reported to decrease after an oral glucose tolerance test in gestational diabetes [190], but not in normal pregnant women [191].…”

Pregnancy and acromegaly: a review

“…In all cases, there was no suppression of GH after OGTT. It should be emphasized that placental GH in normal pregnancy is also not suppressible [14] so that the GH response to OGTT using a non-specific GH assay can be difficult to interpret.…”