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Twenty-four hour hormone profiles of TSH, Free T3 and free T4 in hypothyroid patients on combined T3/T4 therapy.
Exp Clin Endocrinol Diabetes. 2007 Apr; 115(4):261-7.EC

Abstract

The benefits of using thyroxine (T4) plus triiodothyronine (T3) in combination in thyroid hormone replacement are unproven but many individuals continue to be treated with this regime. When T3 is used alone for hypothyroidism, it results in wide fluctuations of thyroid hormone levels. However, only limited data exists on combined T3/T4 therapy. In this study, we have compared 24-hour profiles of thyroid stimulating hormone (TSH), free T4 (fT4) and free T3 (fT3) and cardiovascular parameters in 10 hypothyroid patients who had been on once daily combined T3/T4 therapy for more than 3 months with 10 patients on T4 alone. Twenty patients, who were part of a larger study, investigating the long-term benefits of combined T3/T4 therapy, were recruited into this sub-study. Over 24-hours, 12 samples were taken for thyroid hormones. Their 24-hour pulse and BP is also monitored on a separate occasion. On T4 alone, a modest 16% rise in fT4 with no change in fT3 was seen in the first 4-hours post-dose. In contrast, on combined treatment, fT3 levels showed a marked rise of 42% within the first 4-hours post-dose (T3/T4:T4=6.24: 4.63 mU/L, p<0.001). Mean exposure to fT3 calculated by area under the curve (AUC) was higher (T3/T4:T4=1148:1062, p<0.0001) on T3. Circadian rhythm of TSH was maintained on both treatments. No difference in pulse or blood pressure over the 24-hours was seen between the groups. Our data suggests that despite chronic combined T3/T4 therapy, wide peak-to-trough variation in fT3 levels persists. Although no immediate cardiovascular effects were seen, the long-term consequences for patients on combined therapy are unknown.

Authors+Show Affiliations

Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, UK.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Randomized Controlled Trial

Language

eng

PubMed ID

17479444

Citation

Saravanan, P, et al. "Twenty-four Hour Hormone Profiles of TSH, Free T3 and Free T4 in Hypothyroid Patients On Combined T3/T4 Therapy." Experimental and Clinical Endocrinology & Diabetes : Official Journal, German Society of Endocrinology [and] German Diabetes Association, vol. 115, no. 4, 2007, pp. 261-7.
Saravanan P, Siddique H, Simmons DJ, et al. Twenty-four hour hormone profiles of TSH, Free T3 and free T4 in hypothyroid patients on combined T3/T4 therapy. Exp Clin Endocrinol Diabetes. 2007;115(4):261-7.
Saravanan, P., Siddique, H., Simmons, D. J., Greenwood, R., & Dayan, C. M. (2007). Twenty-four hour hormone profiles of TSH, Free T3 and free T4 in hypothyroid patients on combined T3/T4 therapy. Experimental and Clinical Endocrinology & Diabetes : Official Journal, German Society of Endocrinology [and] German Diabetes Association, 115(4), 261-7.
Saravanan P, et al. Twenty-four Hour Hormone Profiles of TSH, Free T3 and Free T4 in Hypothyroid Patients On Combined T3/T4 Therapy. Exp Clin Endocrinol Diabetes. 2007;115(4):261-7. PubMed PMID: 17479444.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Twenty-four hour hormone profiles of TSH, Free T3 and free T4 in hypothyroid patients on combined T3/T4 therapy. AU - Saravanan,P, AU - Siddique,H, AU - Simmons,D J, AU - Greenwood,R, AU - Dayan,C M, PY - 2007/5/5/pubmed PY - 2007/9/13/medline PY - 2007/5/5/entrez SP - 261 EP - 7 JF - Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association JO - Exp Clin Endocrinol Diabetes VL - 115 IS - 4 N2 - The benefits of using thyroxine (T4) plus triiodothyronine (T3) in combination in thyroid hormone replacement are unproven but many individuals continue to be treated with this regime. When T3 is used alone for hypothyroidism, it results in wide fluctuations of thyroid hormone levels. However, only limited data exists on combined T3/T4 therapy. In this study, we have compared 24-hour profiles of thyroid stimulating hormone (TSH), free T4 (fT4) and free T3 (fT3) and cardiovascular parameters in 10 hypothyroid patients who had been on once daily combined T3/T4 therapy for more than 3 months with 10 patients on T4 alone. Twenty patients, who were part of a larger study, investigating the long-term benefits of combined T3/T4 therapy, were recruited into this sub-study. Over 24-hours, 12 samples were taken for thyroid hormones. Their 24-hour pulse and BP is also monitored on a separate occasion. On T4 alone, a modest 16% rise in fT4 with no change in fT3 was seen in the first 4-hours post-dose. In contrast, on combined treatment, fT3 levels showed a marked rise of 42% within the first 4-hours post-dose (T3/T4:T4=6.24: 4.63 mU/L, p<0.001). Mean exposure to fT3 calculated by area under the curve (AUC) was higher (T3/T4:T4=1148:1062, p<0.0001) on T3. Circadian rhythm of TSH was maintained on both treatments. No difference in pulse or blood pressure over the 24-hours was seen between the groups. Our data suggests that despite chronic combined T3/T4 therapy, wide peak-to-trough variation in fT3 levels persists. Although no immediate cardiovascular effects were seen, the long-term consequences for patients on combined therapy are unknown. SN - 0947-7349 UR - https://www.unboundmedicine.com/medline/citation/17479444/Twenty_four_hour_hormone_profiles_of_TSH_Free_T3_and_free_T4_in_hypothyroid_patients_on_combined_T3/T4_therapy_ L2 - http://www.thieme-connect.com/DOI/DOI?10.1055/s-2007-973071 DB - PRIME DP - Unbound Medicine ER -