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J Clin Endocrinol Metab. 2011 Nov;96(11):3466-74. doi: 10.1210/jc.2011-1329. Epub 2011 Aug 24.

Metabolic effects of liothyronine therapy in hypothyroidism: a randomized, double-blind, crossover trial of liothyronine versus levothyroxine.

Author information

  • 1Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 10, CRC, Room 6-3940, 10 Center Drive, MSC 1613, Bethesda, Maryland 20892-1613, USA. fc93a@nih.gov

Abstract

CONTEXT:

Levothyroxine (L-T(4)) therapy is based on the assumption that the conversion of T(4) into T(3) provides adequate amounts of active hormone at target tissues. However, in rodents, L-T(4) alone does not restore a euthyroid state in all tissues. Previous combination L-T(4)/liothyronine (L-T(3)) therapy trials focused on quality-of-life endpoints, and limited information is available on the effects on other measures of thyroid hormone action.

OBJECTIVE:

Our objective was to evaluate the efficacy of thyroid hormone replacement with L-T(4) or L-T(3) at doses producing equivalent normalization of TSH.

PARTICIPANTS, DESIGN, AND SETTING:

Fourteen hypothyroid patients participated in this randomized, double-blind, crossover intervention at the National Institutes of Health Clinical Center.

INTERVENTIONS:

L-T(3) or L-T(4) were administered thrice daily to achieve a target TSH from 0.5-1.5 mU/liter. Volunteers were studied as inpatients after 6 wk on a stable dose and at the target TSH.

MAIN OUTCOME MEASURES:

Serum thyroid hormones, lipid parameters, and indices of glucose metabolism were evaluated.

RESULTS:

No difference was observed in TSH between L-T(3) and L-T(4) treatments. L-T(3) resulted in significant weight loss [L-T(4), 70.6 ± 12.5, vs. L-T(3), 68.5 ± 11.9 kg (P = 0.009)] and in a 10.9 ± 10.0% decrease in total cholesterol (P = 0.002), 13.3 ± 12.1% decrease in low-density lipoprotein-cholesterol (P = 0.002), and an 18.3 ± 28.6% decrease in apolipoprotein B (P = 0.018). No significant differences were observed in high-density lipoprotein-cholesterol, heart rate, blood pressure, exercise tolerance, or insulin sensitivity.

CONCLUSIONS:

The substitution of L-T(3) for L-T(4) at equivalent doses (relative to the pituitary) reduced body weight and resulted in greater thyroid hormone action on the lipid metabolism, without detected differences in cardiovascular function or insulin sensitivity.

PMID:
21865366
[PubMed - indexed for MEDLINE]
PMCID:
PMC3205882
Free PMC Article

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