This protocol addresses the management of secondary hypothyroidism in a pregnant patient who has pre-existing hypothyroidism and is currently maintained on a stable levothyroxine regimen. Pregnancy creates additional thyroid demands that require a structured response.
Once pregnancy is confirmed in a patient with existing hypothyroidism on stable levothyroxine, thyroid hormone requirements increase beyond the pre-pregnancy baseline. Timely adjustment and close monitoring are essential to support both maternal health and fetal development throughout the pregnancy.
Management involves a structured upward adjustment to the patient's existing levothyroxine therapy. The complete regimen — including the specific adjustment method and monitoring schedule — is available in the full protocol below.
The treatment target is a thyroid-stimulating hormone (TSH) level within the pregnancy-specific reference range. TSH should be assessed at the first prenatal visit and then at regular intervals throughout the pregnancy.
Once pregnancy is confirmed, patients with existing hypothyroidism should start taking an extra dose of levothyroxine two days per week for a total of nine doses per week.
Women with hypothyroidism who become pregnant should increase their weekly dosage by 30% up to nine doses per week (i.e., take one extra dose twice per week), followed by monthly evaluation and management.
Further treatment is guided by measuring TSH levels at the first prenatal visit, then every four weeks with titration of levothyroxine according to the pregnancy-specific TSH reference range.
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