Calcium-regulating hormones and osteocalcin levels during pregnancy: a longitudinal study

Article Abstract:

The effects of pregnancy on calcium levels in the mother are not known. The bone protein osteocalcin is released into the bloodstream in relation to new bone formation. Osteocalcin levels, which are used as a measure of bone metabolism, are lower in pregnant women than in nonpregnant women. The production of osteocalcin is regulated by the parathyroid hormone and 1,25-dihydroxyvitamin D, or 1,25(OH)2D, which increases during pregnancy. Factors other than 1,25(OH)2D and parathyroid hormone may influence osteocalcin levels during pregnancy. Some studies have reported a decrease in parathyroid hormone levels, which may cause the decrease in osteocalcin levels. The changes in osteocalcin levels during pregnancy and the causes of these changes were assessed by measuring blood levels of calcium, phosphorus, calcium-regulating hormones such as parathyroid hormone, and osteocalcin in 20 women throughout their pregnancies. The levels of 1,25(OH)2D were increased in early pregnancy and continued to rise throughout pregnancy. Both parathyroid and osteocalcin levels were low in early pregnancy, declined towards mid pregnancy, and then increased in late pregnancy. The level of osteocalcin correlated with that of parathyroid hormone. These findings are consistent with a regulatory effect of parathyroid hormone and 1,25(OH)2D on osteocalcin. The low levels of this bone protein in early pregnancy are due to low parathyroid hormone levels, which may override the effects of increased 1,25(OH)2D levels. A rise in osteocalcin levels in late pregnancy may result from increases in both 1,25(OH)2D and parathyroid hormone. (Consumer Summary produced by Reliance Medical Information, Inc.)

Measurement, Hormones

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Changes in protein C and protein S levels in normal pregnancy

Article Abstract:

Blood serum levels of free protein S fall during the second trimester of pregnancy, but concentrations of protein C do not vary. Proteins C and S inhibit blood clotting. Deficiency of either one results in increased incidence of venous blood clots. Blood was drawn from 91 healthy pregnant women ranging from 8 weeks to 36 weeks gestation. Protein C levels did not change during pregnancy. Protein S is found both free, bound to another protein, and as a co-factor for protein C. Total levels of protein S were unchanged, but free protein S decreased in concentration during the second trimester. This suggests that when protein S deficiency is suspected, as may happen when pregnant women develop deep venous clots, diagnosis should wait until after pregnancy. Abnormally low protein C levels in pregnancy are more suggestive of protein C deficiency, but, even so, until these data are confirmed, it is best to test after pregnancy.

Risk factors, Thrombosis, Deep vein, Deep vein thrombosis, Protein C, Protein S

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Longitudinal study of beta- and alpha-adrenergic receptor properties during human pregnancy

Article Abstract:

Pregnancy does not seem to alter beta- and alpha-adrenergic receptor characteristics. These receptors are binding sites for counter-reacting hormones involved in muscle contraction and relaxation. Blood samples from 21 women were tested for beta- and alpha-adrenergic characteristics at four time points throughout pregnancy and three and four months after delivery. No characteristic measured, including receptor activity and number, changed significantly throughout the study period.

Epinephrine, Adrenergic receptors

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