Changes in Maternal Serum Aldosterone, Potassium and Prolactin Levels during β-Receptor Agonist Treatment in Third Trimester Pregnancies

Summary

β-receptor agonist (terbutalin or isoxsuprin) administration to pregnant women either because of premature labor (therapy group; T; n = 8) or as prophylactic treatment (prophylaxis group; P; n = 8) resulted in a marked drop in serum potassium (p < 0.001) during the first two hours of infusion in all patients. In five diabetic women in the P group the prolactin was significantly decreased (p < 0.01) as was serum aldosterone levels (p < 0.01). These changes were not observed in the T group. The two groups of pregnant women responded with a significant increase in free fatty acids (FFA) and glucose but the magnitude and the time coarse differed. Thus in T women, FFA reached a peak after 30-60 minutes into treatment and then returned to baseline levels. A closer analysis revealed that this pattern was only obtained in patients receiving terbutalin. Among women given prophylactic treatment with terbutalin, a continuous increase in FFA was noted over the initial two hours (p < 0.001). The increase in serum glucose was continuous in the two patient groups (p < 0.001). It is suggested that β-receptor agonists in diabetic women induces a dopaminergic type of response since serum prolactin levels but not TSH concentrations were affected. The possibility that an increased PGE₂ synthesis at the expense of PGF_2α might mediate this effect of beta;-receptor agonists is discussed. It is also suggested that an increased prostaglandin synthesis might interfere with aldosterone secretion. The possibility that falling serum potassium levels may activate dopaminergic systems via PGE₂ synthesis is also emphasized.

Key-Words:

Pregnancy - Cortisol - Aldosterone - Potassium - Prolactin - TSH - FFA - Glucose - β-Receptor - Agonist - Premature Labor - Diabetic