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.

Key words

Somatotropin - Placenta - Pregnancy - Birthweight - Regulation

References

• 1 Frankenne F, Closset J, Gomez F, Scippo M L, Smal J, Hennen G. The physiology of growth hormones (GHs) in pregnant women and partial characterization of the placental GH variant.  J Clin Endocrinol Metab. 1988;  66 1171-1180
• 2 Barnard R, Chan F-Y, Mclntyre H D. Growth hormone-binding protein in normal and pathological gestation: correlations with maternal diabetes and fetal growth.  J Clin Endocrinol Metab. 1997;  82 1879-1884
• 3 Mclntyre H, Serek R, Crane D I, Veveris-Lowe T, Parry A, Johnson S, Leung K C, Ho K KY, Bougoussa M, Hennen G, Igout A, Chan F-Y, Cowley D, Cotterill A, Barnard R. Placental growth hormone (GH), GH-binding protein and insulin-like growth factor axis in normal, growth-retarded and diabetic pregnancies: correlations with fetal growth.  J Clin Endocrinol Metab. 2000;  85 1143-1150
• 4 Patel N, Alsat A, Igout A, Baron F, Hennen G, Porquet D, Evain-Brion D. Glucose inhibits placental GH secretion, in vitro.  J Clin Endocrinol Metab. 1995;  80 1743-1746
• 5 Alsat E, Guibourdenche J, Couturier A, Evain-Brion D. Physiological role of placental growth hormone.  Mol Cell Endocrinol. 1998;  140 121-127
• 6 Nasrat H A, Ardawi M S, Sabbagh S A. Loss of growth hormone responsiveness to normal physiological stimuli during pregnancy.  J Gynecol Obstet Invest. 1991;  32 148-152
• 7 Björklund A O, Adamson U KC, Carlström K AM, Hennen G, Igout A, Lins P ES, Westgren L MR. Placental hormones during induced hypoglycaemia in pregnancy women with insulin-dependent diabetes mellitus: evidence of an active role for placenta in hormonal counter-regulation.  Br J Obstet Gynaecol. 1998;  105 649-655
• 8 Evain-Brion D, Alsat E, Igout A, Frankenne F, Hennen G. Placental growth hormone variant: assay and clinical aspects.  Acta Paediatr. 1994;  83 (Suppl. 399) 49-51
• 9 Barsano C P, Baumann G. Editorial: simple algebraic and graphic methods for the apportionment of hormone (and receptor) into bound and free fractions in binding equilibria; or how to calculate bound and free hormone?.  Endocrinology. 1989;  124 1101-1106
• 10 Barnard R, Quirk P, Waters M J. Characterization of the growth hormone-binding protein of human serum using a panel of monoclonal antibodies.  J Endocrinol. 1989;  123 327-332
• 11 Hoffman L, Nolan C, Wilson J D, Oats J, Simmons D. Gestational diabetes mellitus - management guidelines. The Australasian Diabetes in Pregnancy Society.  Med J Aust July 20,. 1998;  169 93-97
• 12 de Zegher F, Vanderschueren-Lodeweyckx M, Spitz B, Faijerson Y, Blomberg F, Beckers A, Hennen G, Frankenne F. Perinatal growth hormone (GH) physiology: effect of GH-releasing factor on maternal and fetal secretion of pituitary and placental GH.  J Clin Endocrinol Metab. 1990;  77 520-522
• 13 Eriksson L, Frankenne F, Eden S, Hennen G, von Schoultz B. Growth hormone 24-h serum profiles during pregnancy - lack of pulsatility for the secretion of the placental variant.  Br J Obstet Gynaecol. 1989;  96 949-953
• 14 Duncan E, Wass J AH. Investigation protocol: Acromegaly and its investigation.  Clin Endocrinol. 1998;  50 285-293
• 15 Mancini A, Zuppi P, Fiumara C. et al . GH Response to oral and intravenous glucose load in acromegalic patients.  Horm Metab Res. 1995;  27 332-335
• 16 Goodman H M, Tai L-R, Ray J, Cooke N E, Liebhaber S A. Human growth hormone variant produces insulin-like and lipolytic responses in rat adipose tissue.  Endocrinol. 1991;  129 1779-1783
• 17 Igout A, Frankenne F, L’Hermite-Baleriaux M, Martin A, Hennen G. Somatogenic and lactogenic activity of the recombinant 22kDa isoform of human placental growth hormone.  Growth Regul. 1995;  5 60-65