But two important studies -- a 2007 study published in the journal Clinical Endocrinology, and a follow-up larger randomized trial reported in the December 2010 issue of the Archives of Internal Medicine -- have found that taking the same dose of levothyroxine (i.e., Synthroid) at bedtime, as compared to first thing in the morning, may be better.
The studies were prompted by observation that some patients had improved thyroid hormone profiles improved after they switched from taking their levothyroxine in the morning, to bedtime.
In 2007, Clinical Endocrinology reported on a small pilot study, which looked at the impact on thyroid hormone profiles by changing the time levothyroxine was taken from early morning to bedtime. They also evaluated the impact of this change on the circadian rhythm of TSH and thyroid hormones and thyroid hormone metabolism. The study, while small (12 subjects), was fairly conclusive in its findings, which the researchers said were “striking” and which have “important consequences for the millions of patients who take l-thyroxine daily.”
Researchers reported that taking medication at bedtime, rather than the morning, results in “higher thyroid hormone concentrations and lower TSH concentrations.” TSH decreased and Free T4 levels rose in all patients by changing thyroxine ingestion from early morning to bedtime and T3 levels rose in all but one subject. And TSH decreased irrespective of the starting TSH levels, suggesting better absorption of the thyroid medication when taken in the evening. Interestingly, the researchers found that the circadian TSH rhythm -- the typical daily fluctuations of TSH that occur during a 24-hour period -- dids not vary.
The researchers suggested several explanations for the results:
- Even when waiting at least 30 minutes to eat, breakfast may be interfering with the intestinal absorption of levothyroxine thyroxine.
- “Bowel motility is slower at night,” which means that it takes longer for the levothyroxine tablet to transit through the intestinal system, resulting in longer exposure to the intestinal wall, and therefore, better uptake of the medication.
- The conversion process of T4 to T3 may be more effective in the evening.
That study was conducted between April 2007 through November 2008m, and the results were reported on in the 2010 Archives of Internal Medicine article. The study was a randomized double-blind crossover trial. Ninety patients completed the trial, which involved a six-month period of taking 1 capsule in the morning and 1 capsule at bedtime, with one capsule active levothyroxine, the other placebo, and a switch at the three-month point. The researchers evaluated thyroid hormone levels, as well as creatinine levels, lipid levels, body mass index, heart rate, and quality of life parameters.
The researchers found that the patients taking nighttime levothyroxine had a drop in TSH of 1.25 -- which is a significant change. They free thyroxine (Free T4) level went up by 0.07 ng/dL, and total triiodothyronine (Total T3) went up by 6.5 ng/dL. According to the researchers, there were no significant changes in the other factors.
The researchers concluded that, given the improvement in thyroid hormone levels, physicians should consider prescribing levothyroxine to be taken at bedtime.
From Mary Shomon: What are the Implications for Thyroid Patients?Taking medication at bedtime instead of in the morning could have major implications for many thyroid patients.
- First, it’s easier, as you don’t have to worry about when to eat breakfast.
- Second, it’s easier to avoid medications, supplements and foods, like calcium, iron, and high-fiber foods that can interfere with thyroid medication absorption.
- Third, coffee drinkers would not have to wait until an hour after their medication to enjoy their first cup.
- Fourth, it might offer some improvement in symptoms to people who are just not getting optimal absorption by taking thyroid medication during the day.
You may want to talk to your practitioner about changing the time you take your levothyroxine (i.e., Synthroid, Levoxyl, Levothroid, Unithroid, Eltroxin) to bedtime, versus morning. And if you decide to change to taking your thyroid medication in the evening, be sure to have your thyroid levels evaluated -- six to eight weeks is a reasonable timeframe -- after you’ve made the switch. The blood test results, along with any improvements or worsening of symptoms, will help you and your doctor to determine if you need to adjust the dosage or timing of your medication.
What About Natural Thyroid and T3 Medications?This study was conducted with levothyroxine -- a synthetic form of the long acting T4/thyroxine thyroid hormone. This form of the hormone must first be converted in the body to the active form (T3), and this can take days. Thyroid drugs that contain T3 -- Cytomel, Thyrolar, and the natural desiccated thyroid drugs like Armour -- are used directly by the body within hours. These drugs were not evaluated in the study, and it's not known if medications containing T3, or natural desiccated thyroid drugs would be better absorbed at night.