Calcium supplements (and calcium-rich foods) significantly impair levothyroxine absorption — reducing effective dose by up to 40%. This is an absorption interaction, not a depletion.
Singh et al. (2000) — calcium carbonate significantly reduced levothyroxine absorption
Inadequate thyroid hormone replacement, persistent hypothyroid symptoms
Take levothyroxine 4+ hours away from calcium supplements. Take thyroid medication on empty stomach, 30–60 min before breakfast.
Discuss with your physician before adjusting supplementation. This is educational content, not medical advice.
Selenium is required for conversion of T4 to active T3 via selenodeiodinases. Deficiency impairs the function of thyroid hormone even when replacement doses are adequate.
Contempré et al. (1991) — selenium required for T4→T3 conversion; standard thyroid physiology
Persistent hypothyroid symptoms despite adequate T4 replacement, Hashimoto's progression
Selenomethionine 100–200mcg daily.
View on Fullscript: Thorne Selenomethionine 200mcgDiscuss with your physician before adjusting supplementation. This is educational content, not medical advice.
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