Context Standard therapy for patients with primary hypothyroidism is replacement
with synthetic thyroxine, which undergoes peripheral conversion to triiodothyronine,
the active form of thyroid hormone. Within the lay population and in some
medical communities, there is a perception that adding synthetic triiodothyronine,
or liothyronine, to levothyroxine improves the symptoms of hypothyroidism
despite insufficient evidence to support this practice.
Objective To evaluate the benefits of treating primary hypothyroidism with levothyroxine
plus liothyronine combination therapy vs levothyroxine monotherapy.
Design, Setting, and Patients Randomized, double-blind, placebo-controlled trial conducted from May
2000 to February 2002 at a military treatment facility that serves active
duty and retired military personnel and their family members. The trial included
a total of 46 patients aged 24 to 65 years with at least a 6-month history
of treatment with levothyroxine for primary hypothyroidism.
Intervention Patients received either their usual dose of levothyroxine (n = 23)
or combination therapy (n = 23), in which their usual levothyroxine dose was
reduced by 50 µg/d and substituted with liothyronine, 7.5 µg,
taken twice daily for 4 months.
Main Outcome Measures Scores on a hypothyroid-specific health-related quality-of-life (HRQL)
questionnaire, body weight, serum lipid levels, and 13 neuropsychological
tests measured before and after treatment.
Results Serum thyrotropin levels remained similar and within the normal range
in both treatment groups from baseline to 4 months. Body weight and serum
lipid levels did not change. The HRQL questionnaire scores improved significantly
in both the control group (23%; P<.001) and the
combination therapy group (12%; P = .02), but these
changes were statistically similar (P = .54). In
12 of 13 neuropsychological tests, outcomes between groups were not significantly
different; the 1 remaining test (Grooved Peg Board) showed better performance
in the control group.
Conclusion Compared with levothyroxine alone, treatment of primary hypothyroidism
with combination levothyroxine plus liothyronine demonstrated no beneficial
changes in body weight, serum lipid levels, hypothyroid symptoms as measured
by a HRQL questionnaire, and standard measures of cognitive performance.