Objective: To compare the effects of a unique fixed combination levothyroxine/liothyronine (LT4/LT3) therapy in patients with primary hypothyroidism. Subjects and methods: This is a randomized, double-blind, crossover study. Adults with primary hypothyroidism (n = 32, age 42.6 ± 13.3, 30 females) on stable doses of LT4 for ≥ 6 months (125 or 150 μg/day) were randomized to continue LT4 treatment (G1) or to start LT4/LT3 therapy (75/15 μg/day; G2). After 8 weeks, participants switched treatments for 8 more weeks. Thyroid function, lipid profile, plasma glucose, body weight, electrocardiogram, vital signs, and quality of life (QoL) were evaluated at weeks 0, 8 and 16. Results: Free T4 levels were significantly lower while on LT4/LT3 (G1: 1.07 ± 0.29 vs. 1.65 ± 0.46; G2: 0.97 ± 0.26 vs. 1.63 ± 0.43 ng/dL; P < 0.001). TSH and T3 levels were not affected by type of therapy. More patients on LT4/ LT3 had T3 levels above the upper limit (15% vs. 3%). The combination therapy led to an increase in heart rate, with no significant changes in electrocardiogram or arterial blood pressure. Lipid profile, body weight and QoL remained unchanged. Conclusions: The combination therapy yielded significantly lower free T4 levels, with no changes in TSH or T3 levels. More patients on LT4/T3 had elevated T3 levels, with no significant alterations in the evaluated outcomes. No clear clinical benefit of the studied formulation could be observed. Future trials need to evaluate different formulations and the impact of the combined therapy in select populations with genetic polymorphisms. Arch Endocrinol Metab. 2016;60(6):562-72
Objective: The aim of the study was to evaluate the effects of usual doses of oral estradiol with transdermal estradiol and the effects of these estrogens plus micronized progesterone (MP) in menopausal women with primary hypothyroidism. Methods: Twenty women were randomized to 12 weeks of treatment with estradiol 1 mg tablets or estradiol 1 mg gel. Then, women with a uterus received a 100 mg capsule of oral MP. Thyroid function, thyroxine-binding globulin (TBG), sex hormone-binding globulin (SHBG), insulin-like growth factor 1 (IGF-1), lipid profiles, and quality of life were measured at baseline and after 12 and 24 weeks. Results: Oral estradiol led to an increase in total T4 levels (5.84 ± 1.11 vs 8.41 ± 1.61 μg/dL; P < 0.001); changes in thyroid-stimulating hormone (TSH) levels were clinically important in 3 of 10 participants who needed to increase their dose of levothyroxine. Significant changes were detected in hepatic proteins with oral estradiol: TBG and SHBG levels increased (15.29 ± 3.87 vs 20.84 ± 5.49 μg/mL, P < 0.001; 61.85 ± 33.6 vs 121.4 ± 49.36 nmol/L, P < 0.001; respectively), whereas IGF-1 levels decreased (152 ± 38.91 vs 96 ± 17.59 ng/mL; P < 0.001). Transdermal estradiol alone did not significantly affect the thyroid function. Transdermal estradiol plus MP led to a decrease in TSH levels (1.79 ± 1.05 vs 1.09 ± 0.52 mIU/L; P = 0.04), while total T4 levels increased (7.54 ± 1.34 vs 9.95 ± 2.24 μg/dL; P = 0.01). Hormonal therapy had a greater impact on depressed mood and vasomotor symptoms. Conclusions: Total T4 and TBG levels increase after oral estradiol in women with hypothyroidism and it may cause clinical changes in TSH levels. Conversely, transdermal estradiol alone or plus MP does not cause major changes in thyroid function in these women. Video Summary: http://links.lww.com/MENO/A783.
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