SFEBES2008 Poster Presentations Thyroid (68 abstracts)
Effects of dietary soy phytoestrogens on thyroid function and insulin resistance in patients with subclinical hypothyroidism: a double blind crossover study
Thozhukat Sathyapalan 1 , Alireza M Manuchehri 1 , Natalie J Thatcher 2 , Don B Clarke 3 , Alan S Rigby 4 , Eric S Kilpatrick 5 , Tom Chapman 6 , Anthony S Lloyd 3 & Stephen L Atkin 1
1Department of Diabetes and Endocrinology, University of Hull, Hull, UK; 2Food Standards Agency, London, UK; 3Food Safety Group, Department for Environment, Food and Rural Affairs, Sand Hutton, York, UK; 4Department of Academic Cardiology, University of Hull, Hull, UK; 5Department of Clinical Biochemistry, Hull Royal Infirmary, Hull, UK; 6Essential Nutrition Ltd, Brough, UK.
Soy phytoestrogens (PE) have been shown to improve insulin resistance and lipids but may adversely affect thyroid function.
Objective: To determine the effects of soy PE on thyroid function, insulin resistance and lipid parameters in patients with subclinical hypothyroidism.
Design: A randomised, double-blind, crossover study was undertaken involving 60 patients with subclinical hypothyroidism. Patients were randomly assigned to either a low dose isoflavone (30 g of soy protein with 2 mg soy isoflavones) or a high dose isoflavone (30 g of soy protein with 16 mg soy isoflavones) supplement for 8 weeks, with 8-week wash out period, before crossover.
Main outcome measures: Changes in thyroid function tests, glucose, insulin (HOMA-IR), lipid profile, hsCRP, and plasma PE before and after treatment with low dose/high dose PE were measured.
Results: There was significant improvement in insulin resistance after 16 mg isoflavone phase (mean±S.D.) (HOMA-IR 5.11±12.2 vs 4.2±9.9 (P value 0.02) 95% CI 0.12–1.63) but no changes after 2 mg isoflavone phase. There were no changes in fT4 and TSH before or after both phases. However, the fT3 values were higher after the initial 16 mg then 2 mg isoflavone treatment (mean±S.D.) (4.11±0.62 vs 4.56±0.65 pmol/l P value <0.01), but not the converse. There were no changes seen in the lipid profiles or hsCRP.
Conclusion: High (16 mg) levels of dietary PE have a significant effect on reducing insulin resistance, but do not affect thyroid function clinically in patients with subclinical hypothyroidism that are iodine replete.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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