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Levothyroxine Dose Adjustment in Pregnant Women With Primary Hypothyroidism


Levothyroxine Dose Adjustment in Pregnant Women With Primary Hypothyroidism

The maternal thyroid hormones have to be strictly regulated during pregnancy for optimal maternal and fetal outcomes.Although there are no specific guidelines addressing maternal levothyroxine (LT4) dose adjustments throughout pregnancy close monitoring of maternal thyroid function is recommended in hypothyroid women during pregnancy.

The American Thyroid Association (ATA) recommends that maternal thyroid-stimulating hormone (TSH) be maintained between 0.1 and 2.5 mIU/L in trimester 1 (T-1), 0.2 and 3.0 mIU/L in trimester 2 (T-2), and 0.3 and 3.0 mIU/L in trimester 3 (T-3) to prevent potential adverse outcomes related to maternal and fetal hypothyroidism. Dr.Shannon D. Sullivan and associates  in Academic endocrinology clinics in Washington, DC compared two LT4 dose-adjustment algorithms in hypothyroid pregnant women and found that an ongoing adjustment approach is as effective as empiric dose increase for maintaining goal TSH in hypothyroid women during pregnancy.The study was published in Journal of  Clinical Endocrinology and  Metabolism.

 The researchers  compared 2 methods for adjusting thyroid medicine during pregnancy in women with known thyroid disease. Pregnant women (age 18 to 45) who take thyroid medication were randomized to either 1) a 2-dose per week increase in thyroid medicine once pregnancy is confirmed, followed by dose adjustments every 2-4 weeks, or 2) adjustments in thyroid medication every 2-4 weeks in micrograms per day based on results of blood tests. The investigators  compared thyroid hormone levels throughout pregnancy between the groups of mothers to determine which method is superior in meeting the increased thyroid hormone requirements during pregnancy.

They recruited thirty-three women on stable LT4 doses were  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.The main outcome measure was  proportion of TSH values within trimester-specific goal ranges and mean gestational age at study entry was 6.4±2.1 weeks .

.It was found that 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.

The authors  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

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Dr. Kamal Kant Kohli

Dr. Kamal Kant Kohli

A Medical practitioner with a flair for writing medical articles, Dr Kamal Kant Kohli joined Medical Dialogues as an Editor-in-Chief for the Speciality Medical Dialogues. Before Joining Medical Dialogues, he has served as the Hony. Secretary of the Delhi Medical Association as well as the chairman of Anti-Quackery Committee in Delhi and worked with other Medical Councils of India. Email: drkohli@medicaldialogues.in. Contact no. 011-43720751
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