Administration of Levothyroxine 45 - 60 Minutes before Breakfast Improves Biochemical Availability as Evidenced by Reduced Thyrotropin Levels

Shivshankar Seechurn, Sanjeev Sharma, Samson Oyibo

Department of Diabetes and Endocrinology, Peterborough City Hospital, Peterborough, UK.

DOI: 10.4236/ojemd.2012.23005                

Abstract

Introduction: Serum Thyrotropin (TSH) level is used to assess adequacy of levothyroxine dosing for patients with hypothyroidism. Some patients have raised TSH levels despite being on an adequate dose of levothyroxine (100 mcg/day - 200 mcg/day). Aim: To evaluated the effect of advising patients to take their levothyroxine 45 - 60 minutes before breakfast on raised serum TSH levels. Patients and Methods: Rather than increase the dose, patients with raised TSH levels were asked to take their levothyroxine at least 45 - 60 minutes before breakfast and other oral medications. Thyroid Function Tests were assessed at base line and repeated after two months. Results: Data from ten patients who presented between 2008 and 2010 were analyzed (9 females, 1 male): With median (IQR) age: 39 (33 - 49) years and duration of hypothyroidism: 6 (3 - 7.8) years. Median (IQR) levothyroxine dose was 175 (144 - 250) mcg, serum free-Thyroxine (free-T4): 13 (10.5 - 17.1) pmol/L and serum TSH: 12.63 (6.2 - 48.3) mIU/L. After two months all patients demonstrated biochemical improvement; a decrease in serum TSH to 3.15 (0.4 - 6.1) mIU/L accompanied by an increase in serum free-T4 to 17.7 (14.8 - 21.3) pmol/L. Both changes were statistically significant (p < 0.05 and p < 0.01, respectively). The median (IQR) percentage TSH reduction was 83.5 (40.3 - 95.8) mIU/L and this bore no significant correlation with the initial TSH level (rs = 0.2, p = 0.58). Conclusion: Changing levothyroxine administration to 45 - 60 minutes before breakfast and other oral medications reduced TSH levels by 40% - 96% in all patients. We recommend this advice for all patients with hypothyroidism on adequate doses of levothyroxine but still appear biochemically under-replaced.

Keywords

Levothyroxine; Thyrotropin; Bioavailability

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	S. K. Grebe, R. R. Cooke and H. C. Ford, “Treatment of Hypothyroidism with Once Weekly Thyroxine,” Journal of Clinical Endocrinology and Metabolism, Vol. 82, No. 3, 1997, pp. 870-875. doi:10.1210/jc.82.3.870
[2]	L. H. Fish, H. L. Schwartz, J. Cavanaugh, M. W. Steffes, J. P. Bantle and J. H. Oppenheimer, “Replacement Dose, Metabolism, and Bioavailability of Levothyroxine in the Treatment of Hypothyroidism. Role of Triiodothyronine in Pituitary Feedback in Humans,” The New England Journal of Medicine, Vol. 316, 1987, pp. 764-770. doi:10.1056/NEJM198703263161302
[3]	K. W. Wenzel and H. E. Kirschsieper, “Aspects of the Absorption of Oral L-Thyroxine in Normal Man,” Metabolism, Vol. 26, No. 1, 1977, pp. 1-8. doi:10.1016/0026-0495(77)90121-4
[4]	B. Vaidya and S. H. Pearce, “Management of Hypothyroidism in Adults,” British Medical Journal, Vol. 337, 2008, pp. a801. doi:10.1136/bmj.a801
[5]	D. S. Bell and F. Ovalle, “Use of Soy Protein Supplement and Resultant Need for Increased Dose of Levothyroxine,” Endocr Pract, Vol. 7, No. 3, 2001, pp. 193-194.
[6]	S. Benvenga, L. Bartolone, M. A. Pappalardo, A. Russo, D. Lapa, G. Giorgianni, G. Saraceno and F. Trimarchi, “Altered Intestinal Absorption of L-Thyroxine Caused by Coffee,” Thyroid, Vol. 18, No. 3, 2008, pp. 293-301. doi:10.1089/thy.2007.0222
[7]	Y. Liel, I. Harman-Boehm and S. Shany, “Evidence for a Clinically Important Adverse Effect of Fiber-Enriched Diet on the Bioavailability of Levothyroxine in Adult Hypothyroid Patients,” Journal of Clinical Endocrinology and Metabolism, Vol. 81, No. 2, 1996, pp. 857-859. doi:10.1210/jc.81.2.857
[8]	N. Bolk, T. J. Visser, A. Kalsbeek, R. T. van Domburg and A. Berghout, “Effects of Evening vs Morning Thyroxine Ingestion on Serum Thyroid Hormone Profiles in Hypothyroid Patients,” Clinical Endocrinology, Vol. 66, 2007, pp. 43-48.
[9]	S. Benvenga, L. Bartolone, S. Squadrito, F. Lo Giudice and F. Trimarchi, “Delayed Intestinal Absorption of Levothyroxine,” Thyroid, Vol. 5, No. 4, 1995, pp. 249-253. doi:10.1089/thy.1995.5.249
[10]	L. Liwanpo and J. M. Hershman, “Conditions and Drugs Interfering with Thyroxine Absorption,” Best Practice and Research Clinical Endocrinology and Metabolism, Vol. 23, No. 6, 2009, pp. 781-792. doi:10.1016/j.beem.2009.06.006
[11]	V. Srinivas and S. O. Oyibo, “Levothyroxine Pseudomalabsorption and Thyroxine Absorption Testing with Use of High-Dose Levothyroxine: Case Report and Discussion,” Endocrine Practice, Vol. 16, No. 6, 2010, pp. 1012-1015. doi:10.4158/EP10224.CR