Thyroid Hormone Medication Should Not Be Taken With Cow’s Milk

MedicalResearch.com Interview with:
Deborah Chon MD
Endocrinology fellow
UCLA David Geffen School of Medicine 

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: Our study shows that drinking cow’s milk concurrently with oral levothyroxine significantly reduces the absorption of the medication.

Levothyroxine is used for the physiologic replacement of thyroid hormone in patients with hypothyroidism and for serum TSH suppression in patients with thyroid cancer. It is the mostly commonly prescribed medication in the United States as of 2014. Frequent dose adjustments of levothyroxine have been shown to be a costly burden to the national healthcare system.

Previous studies have shown that certain foods and medication, such as calcium supplements, can interfere with levothyroxine absorption. However, this is the first study to demonstrate that ingesting cow?s milk, a common breakfast staple, affects oral levothyroxine absorption.

To determine the possible effect of cow’s milk ingestion, we measured levothyroxine absorption in humans with and without concurrent milk consumption. Pharmacokinetic studies were conducted in healthy adults without allergies to milk or levothyroxine, and who were not pregnant nor using oral contraceptives. All subjects had no history of known thyroid disease and normal thyroid hormone function at baseline. Following an overnight fast, serum total thyroxine T4 (TT4) concentrations were measured at baseline and at 1, 2, 4, and 6 hours after ingestion of 1,000 ?g of oral levothyroxine alone or when co-administered with 12 oz. of milk (2% fat). There was a four-week washout period between the two study visits.

Ten subjects (mean age 33.7?10.2 years, 60% male) completed the study. The serum total T4 absorption over six hours, calculated as area under the curve (AUC), was significantly lower when taking cow?s milk concurrently with levothyroxine compared levothyroxine alone (mean?SD: 67.26?12.13 vs. 73.48?16.96; p = 0.02). Also, peak serum TT4 concentrations were significantly lower in those who ingested levothyroxine concurrently with milk, compared to taking levothyroxine alone (p=0.04).

MedicalResearch.com: What should readers take away from your report?

Response: Patients managed with thyroid hormone should be advised not to drink cow’s milk simultaneously with oral levothyroxine.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Response: Future studies could evaluate the amount of time after which milk no longer interferes with levothyroxine absorption. Also, different types of milk, such as soy milk, almond milk, etc. could be studied to evaluate if they have an effect on levothyroxine absorption.

All those involved in this study have no disclosures.

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.

Citation:

ENDO 2017 abstract:

Concurrent Milk Ingestion Decreases Oral Levothyroxine Absorption
Deborah Chon*1, Tamar Reisman2, Jane Weinreb3, Jerome M Hershman1 and Angela M. Leung4
1UCLA David Geffen School of Medicine; VA Greater Los Angeles Healthcare System, Los Angeles, CA, 2UCLA David Geffen School of Medicine; VA Greater Los Angeles Healthcare System, 3David Geffen School of Medicine at UCLA; VA Greater Los Angeles Healthcare System, Los Angeles, CA, 4UCLA David Geffen School of Medicine, Los Angeles, CA

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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