Thyroid Medications
Common brand names: Synthroid, Levothyroxine, Armour Thyroid
Two nutrients listed against this medication. The most severe is marked critical.
At a glance
One of the two is marked well documented. The other one carries its own evidence level.
At a glance
- Calcium (Important: Interaction)Critical · Well documented
- SeleniumModerate · Traditionally cited, limited evidence
Color shows how serious each listed effect is. The label beside it shows how strong the evidence is. The cards below explain each one and show its evidence.
Nutrients it can lower
Mechanism, Calcium supplements (and calcium-rich foods) significantly impair levothyroxine absorption, reducing the effective dose substantially. Background figure, not from a trial cited on this record. This is an absorption interaction, not a depletion.
Common signs, Inadequate thyroid hormone replacement, persistent hypothyroid symptoms
Singh et al. (2000; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 10838651): calcium carbonate significantly reduced levothyroxine absorption
Levothyroxine is separated from calcium supplements by at least 4 hours and taken on an empty stomach, 30–60 minutes before breakfast.
Mechanism, 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.
Common signs, Persistent hypothyroid symptoms despite adequate T4 replacement, Hashimoto's progression
Selenium supports T4→T3 conversion (physiology); the cited Contempré work concerns selenium deficiency in iodine-deficient regions, not levothyroxine-caused depletion.
Selenomethionine 100–200 mcg daily is a range in common use, not from a trial cited on this row. The cited work concerns selenium deficiency in iodine-deficient regions, not levothyroxine-caused depletion.
For your next appointment
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Disclosure
These statements have not been evaluated by the Food and Drug Administration. Any grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
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