The effect of soy phytoestrogen supplementation on thyroid status and cardiovascular risk markers in patients with subclinical hypothyroidism: A randomized, double-blind, crossover study

Sathyapalan, Thozhukat; Manuchehri, Alireza M.; Thatcher, Natalie J.; Rigby, Alan S.; Chapman, Tom; Kilpatrick, Eric S.; Atkin, Stephen L.

Abstract

Context: There is concern whether soy phytoestrogens may affect thyroid function. If true, soy phytoestrogens may be expected to have a greater impact in subjects with subclinical hypothyroidism. Objective: The primary aim was to determine the effect of soy phytoestrogen supplementation on thyroid function, with a secondary aim of assessing the effects on cardiovascular risk indices in patients with subclinical hypothyroidism. Design and Setting: We conducted a randomized, double-blind, crossover study in a tertiary care setting. Participants: Sixty patients with subclinical hypothyroidism participated in the study. Intervention: Patients were randomly assigned to either low-dose phytoestrogen (30 g soy protein with 2 mg phytoestrogens, representative of a Western diet) or high-dose phytoestrogen (30 g soy protein with 16 mg phytoestrogens, representative of a vegetarian diet) supplementation for 8 wk, then crossed over after an 8-wk washout period. Main Outcome Measures: The primary outcome was progression to overt hypothyroidism, with secondary outcome measures of blood pressure, insulin resistance, lipids, and highly sensitive C-reactive protein (hsCRP). Results: Six female patients in the study progressed into overt hypothyroidism with a standardized rate ratio of 3.6 (95% confidence interval, 1.9, 6.2) after 16-mg phytoestrogen supplementation. Both systolic and diastolic blood pressure decreased with 16 mg phytoestrogens, whereas systolic pressure alone decreased with 2 mg phytoestrogens. Insulin resistance (homeostasis model assessment of insulin resistance, 3.5 ± 0.09 vs. 2.6 ± 0.08; P < 0.02) and hsCRP (4.9 ± 0.04 vs. 3.9 ± 0.03; P < 0.01) decreased with 16 mg phytoestrogens. Lipid profile remained unchanged. Conclusion: There is a 3-fold increased risk of developing overt hypothyroidism with dietary supplementation of 16 mg soy phytoestrogens with subclinical hypothyroidism. However, 16-mg soy phytoestrogen supplementation significantly reduces the insulin resistance, hsCRP, and blood pressure in these patients. Copyright © 2011 by The Endocrine Society.

Citation

Sathyapalan, T., Manuchehri, A. M., Thatcher, N. J., Rigby, A. S., Chapman, T., Kilpatrick, E. S., & Atkin, S. L. (2011). The effect of soy phytoestrogen supplementation on thyroid status and cardiovascular risk markers in patients with subclinical hypothyroidism: A randomized, double-blind, crossover study. Journal of Clinical Endocrinology and Metabolism, 96(5), 1442-1449. https://doi.org/10.1210/jc.2010-2255

• Journal Article Type: Article
• Acceptance Date: Jan 24, 2011
• Publication Date: May 1, 2011
• Deposit Date: Nov 13, 2014
• Publicly Available Date: Nov 13, 2014
• Journal: Journal of clinical endocrinology & metabolism
• Print ISSN: 0021-972x
• Publisher: Oxford University Press
• Peer Reviewed: Not Peer Reviewed
• Volume: 96
• Issue: 5
• Pages: 1442-1449
• DOI: https://doi.org/10.1210/jc.2010-2255
• Keywords: Clinical Biochemistry; Biochemistry; Endocrinology, Diabetes and Metabolism; Endocrinology; Biochemistry, medical
• Public URL: https://hull-repository.worktribe.com/output/463243
• Publisher URL: http://press.endocrine.org/doi/abs/10.1210/jc.2010-2255
• Additional Information: Copy of article first published in Journal of clinical endocrinology & metabolism
• Contract Date: Nov 13, 2014