Citation: Journal of Clinical Endocrinology & Metabolism. 102(9):3499-3507, 2017 Sep 01.Journal: The Journal of clinical endocrinology and metabolism.Published: 2017ISSN: 0021-972X.Full author list: Sullivan SD; Downs E; Popoveniuc G; Zeymo A; Jonklaas J; Burman KD.UI/PMID: 28911144.Subject(s): IN PROCESS -- NOT YET INDEXEDInstitution(s): MedStar Washington Hospital CenterDepartment(s): Medicine/EndocrinologyActivity type: Journal Article.Medline article type(s): Journal ArticleOnline resources: Click here to access onlineDigital Object Identifier: https://dx.doi.org/10.1210/jc.2017-01086 (Click here)Abbreviated citation: J Clin Endocrinol Metab. 102(9):3499-3507, 2017 Sep 01.Local Holdings: Available online through MWHC library: 1999- June 2013, Available in print through MWHC library: 1999 - 2006.Abstract: Context: Regulation of maternal thyroid hormones during pregnancy is crucial for optimal maternal and fetal outcomes. There are no specific guidelines addressing maternal levothyroxine (LT4) dose adjustments throughout pregnancy.Abstract: Objective: To compare two LT4 dose-adjustment algorithms in hypothyroid pregnant women.Abstract: Design: Thirty-three women on stable LT4 doses were recruited at <10 weeks gestation during 38 pregnancies and randomized to one of two dose-adjustment groups. Group 1 (G1) used an empiric two-pill/week dose increase followed by subsequent pill-per-week dose adjustments. In group 2 (G2), LT4 dose was adjusted in an ongoing approach in micrograms per day based on current thyroid stimulating hormone (TSH) level and LT4 dose. TSH was monitored every 2 weeks in trimesters 1 and 2 and every 4 weeks in trimester 3.Abstract: Setting: Academic endocrinology clinics in Washington, DC.Abstract: Main Outcome Measure: Proportion of TSH values within trimester-specific goal ranges.Abstract: Results: Mean gestational age at study entry was 6.4 +/- 2.1 weeks. Seventy-five percent of TSH values were within trimester-specific goal ranges in G1 compared with 81% in G2 (P = 0.09). Similar numbers of LT4 dose adjustments per pregnancy were required in both groups (G1, 3.1 +/- 2.0 vs G2, 4.1 +/- 3.2; P = 0.27). Women in G1 were more likely to have suppressed TSH <0.1 mIU/L in trimester 1 (P = 0.01). Etiology of hypothyroidism, but not thyroid antibody status, was associated with proportion of goal TSH values.Abstract: Conclusions: We compared two options for LT4 dose adjustment and showed that an ongoing adjustment approach is as effective as empiric dose increase for maintaining goal TSH in hypothyroid women during pregnancy.