Efficacy of a Levothyroxine Dosage Regimen Based on Serum Thyrotropin Level, for Primary Hypothyroidism. An Open Label Dose Finding Study

Overview

Journal J Family Med Prim Care

Specialty Public Health

Date 2024 Mar 14

PMID 38482303

Authors

Abilash Nair

Jayakumari Chellamma

Anjana Gopi

Chintha Sujatha

Soumya Sarayu

P K Jabbar

Affiliations

Soon will be listed here.

Abstract

Background: There are no guidelines on individualized initial levothyroxine dosage in primary hypothyroidism. This prospective observational study was done to assess whether a predetermined dose of levothyroxine based on Thyroid Stimulating Hormone (TSH) levels would be able to make the patient euthyroid during a period of six weeks and to find other factors which influence the levothyroxine requirement.

Materials And Methods: Newly diagnosed patients with primary hypothyroidism or those patients who were not on levothyroxine therapy were divided into TSH-based groups-Group 1, 5-9.99, Group 2, 10-29.99, Group 3, 30-99.99 and Group 4, >100 μIU/ml and treated with an initial levothyroxine dose of 25,50,75 and100 μg/day for next six weeks. Factors correlating with levothyroxine requirement were determined.

Results: Of the 171 patients who were included 142 completed the study, 34,46,28 and 34 patients were included in groups 1 to 4, respectively. Normalization of TSH with the above criteria was achieved in 111 (78.7%) out of 141 patients, and 91%, 67%, 75%, and 82% respectively in the 4 groups. Among adequately replaced patients pre-treatment TSH level (r = 0.81), T4 level (r = 0.61), and body weight (r = 0.19) correlated with the levothyroxine requirement. Based on these factors predicted initial dose (μg/day) was found to be 0.54 (Body Weight [Kg]) +0.47 (TSH [μIU/m]) - 1.4 (Total T4 [μg/dl]) +17.79 or 0.27 (Body Weight) +0.553 (TSH) +21.

Conclusion: Serum thyrotropin-based categorization for initial levothyroxine dose leads to euthyroidism in nearly four of five patients with primary hypothyroidism. The dose required for adequate replacement of levothyroxine has correlation with pre-treatment serum TSH levels serum thyroxine levels and body weight.

References

Rink T, Schroth H, Holle L, Garth H . [Individual calculation of the minimal effective levothyroxine dose in prolonged suppression tests]. Nuklearmedizin. 1998; 37(6):197-201. View

Rosenbaum R, BARZEL U . Levothyroxine replacement dose for primary hypothyroidism decreases with age. Ann Intern Med. 1982; 96(1):53-5. DOI: 10.7326/0003-4819-96-1-53. View

Gordon M, Gordon M . Variations in adequate levothyroxine replacement therapy in patients with different causes of hypothyroidism. Endocr Pract. 2004; 5(5):233-8. DOI: 10.4158/EP.5.5.233. View

Jonklaas J, Bianco A, Bauer A, Burman K, Cappola A, Celi F . Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014; 24(12):1670-751. PMC: 4267409. DOI: 10.1089/thy.2014.0028. View

Kabadi U . Optimal daily levothyroxine dose in primary hypothyroidism. Its relation to pretreatment thyroid hormone indexes. Arch Intern Med. 1989; 149(10):2209-12. View

Chiovato L, Magri F, Carle A . Hypothyroidism in Context: Where We've Been and Where We're Going. Adv Ther. 2019; 36(Suppl 2):47-58. PMC: 6822815. DOI: 10.1007/s12325-019-01080-8. View

Fish L, Schwartz H, Cavanaugh J, Steffes M, Bantle J, OPPENHEIMER J . Replacement dose, metabolism, and bioavailability of levothyroxine in the treatment of hypothyroidism. Role of triiodothyronine in pituitary feedback in humans. N Engl J Med. 1987; 316(13):764-70. DOI: 10.1056/NEJM198703263161302. View

DAVIS F, LaMantia R, Spaulding S, Wehmann R, Davis P . Estimation of a physiologic replacement dose of levothyroxine in elderly patients with hypothyroidism. Arch Intern Med. 1984; 144(9):1752-4. View

Singh R, Tandon A, Awasthi A . Development and Prospective Validation of the Levothyroxine Dose Prediction Model in Primary Hypothyroidism. Horm Metab Res. 2021; 53(4):264-271. DOI: 10.1055/a-1336-3502. View

10.

Kabadi U . 'Subclinical hypothyroidism'. Natural course of the syndrome during a prolonged follow-up study. Arch Intern Med. 1993; 153(8):957-61. DOI: 10.1001/archinte.153.8.957. View

11.

Mandel S, Brent G, Larsen P . Levothyroxine therapy in patients with thyroid disease. Ann Intern Med. 1993; 119(6):492-502. DOI: 10.7326/0003-4819-119-6-199309150-00009. View

12.

Santini F, Pinchera A, Marsili A, Ceccarini G, Castagna M, Valeriano R . Lean body mass is a major determinant of levothyroxine dosage in the treatment of thyroid diseases. J Clin Endocrinol Metab. 2004; 90(1):124-7. DOI: 10.1210/jc.2004-1306. View

13.

Kabadi U . Influence of age on optimal daily levothyroxine dosage in patients with primary hypothyroidism grouped according to etiology. South Med J. 1997; 90(9):920-4. DOI: 10.1097/00007611-199709000-00012. View

14.

Roos A, Linn-Rasker S, van Domburg R, Tijssen J, Berghout A . The starting dose of levothyroxine in primary hypothyroidism treatment: a prospective, randomized, double-blind trial. Arch Intern Med. 2005; 165(15):1714-20. DOI: 10.1001/archinte.165.15.1714. View

15.

Singh R . Does One Size Fit Everyone? Replacement Dose of Levothyroxine in Long-standing Primary Hypothyroidism in Adults. Indian J Endocrinol Metab. 2017; 21(3):404-409. PMC: 5434723. DOI: 10.4103/ijem.IJEM_502_16. View

16.

Devdhar M, Drooger R, Pehlivanova M, Singh G, Jonklaas J . Levothyroxine replacement doses are affected by gender and weight, but not age. Thyroid. 2011; 21(8):821-7. PMC: 3148125. DOI: 10.1089/thy.2011.0029. View

17.

Kabadi U, Jackson T . Serum thyrotropin in primary hypothyroidism. A possible predictor of optimal daily levothyroxine dose in primary hypothyroidism. Arch Intern Med. 1995; 155(10):1046-8. View