title: Chronic levothyroxine and acute T3 treatments enhance the amplitude and time course of uterine contractions in human.
abstract: This study compares the functional consequences of levothyroxine (T4) treatment during pregnancy as well as the acute affects of triiodothyronine (T3) on spontaneous uterine contractile activities observed in vitro. Uterine biopsies were obtained from consenting women undergoing elective caesarean at term (n = 28). Spontaneous contractile activities from T4-treated pregnant women (n = 8) were compared with control patients (n = 20) by isometric tension measurements. Effects of acute T3 and T4 on control tissues were also monitored. Area under the curve, amplitude, time to peak, duration, and frequency were quantified. In uterine strips from women treated for hypothyroidism, phasic uterine contractions of larger amplitude (+77%) were observed, with a prolonged duration at 90% relaxation (+138%) and reduced frequency (-55%) compared with values of the control group. The addition of exogenous T3 in vitro on control strips induced a significant increase in the duration of the contractions and a significant decrease in frequency (P < 0.05), which partially mimics the results obtained in strips from T4-treated women. Significant modifications of contractile properties were observed in strips from pregnant women treated with levothyroxine, consistent with those observed with the addition of exogenous T3. Clinical practices of modern obstetrics should take into account the effect of thyroid hormones on uterine contractions' time course to ensure a tighter followup at the end of pregnancy to achieve safer delivery.
authors.affiliation: Department of Obstetrics and Gynecology, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Corriveau
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Pasquier
authors.forename: Simon
authors.initials: S
authors.lastname: Blouin
authors.forename: Diego
authors.initials: D
authors.lastname: Bellabarba
authors.forename: Éric
authors.initials: É
authors.lastname: Rousseau
mesh_terms: D000328:Adult; D015153:Blotting, Western; D002585:Cesarean Section; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000503:physiopathology; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000187:drug effects; D009215:Myometrium / Q000187:drug effects; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011247:Pregnancy; D013347:Subcellular Fractions / Q000378:metabolism; D013974:Thyroxine / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects*; D055815:Young Adult
chemical_list: D026902:Potassium Channel Blockers; D014284:Triiodothyronine; D013974:Thyroxine