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6.2.1 Hypothyroidism

Formulary choiceLevothyroxine tablets 25micrograms, 50micrograms, 100 micrograms

Prescribing Notes

  • Refer to NICE NG145 Thyroid disease: assessment and management.
  • Prior to treatment, it is important to establish that thyroid stimulating hormone (TSH) is elevated, thus confirming primary hypothyroidism. A normal or low TSH may suggest pituitary or hypothalamic disease for which specialist referral is necessary.

Levothyroxine monitoring (see SPS for full details):

  • After started or dose changed:
    • TSH from 6 weeks; repeated every 3 months
    • Consider (where symptoms are ongoing) – free T4 from 6 weeks; repeated every 3 months
  • Ongoing once stable (2 similar measurements within the reference range, 3 months apart); TSH annually.
  • Alteration in levothyroxine absorption may occur with introduction of other medication such as iron and calcium preparations or drugs altering gastric acid, such as proton pump inhibitors. Thyroid function should be checked 6 weeks after starting such treatment.
  • Pregnant patients with hypothyroidism should be referred to a specialist for titration of levothyroxine regimens, although it is recommended that upon confirmation of pregnancy, due to the early increase in levothyroxine requirements, levothyroxine dosage is doubled on Saturdays and Sundays until early review by a specialist.
  • Although generic prescribing remains appropriate for the majority of patients, a small proportion report re-emergence of symptoms after switching between levothyroxine products and hence may benefit from consistent prescribing of a specific brand. See MHRA for further information.
  • Levothyroxine liquid is significantly more expensive than levothyroxine tablets. Therefore, tablets are the preferred formulation, where appropriate.
  • Liothyronine should only be used on the recommendation of a Health Service endocrine specialist in secondary care; prescribers in primary care should not initiate liothyronine. For further information please see Shared Care Guideline.
  • Where prescribing of liothyronine is appropriate, the initiating specialist in secondary care should recommend prescribing of liothyronine capsules instead of tablets. For further information refer to SPPG letter.