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.
RCT Entities:
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.
Authors: Jacqueline Jonklaas; Antonio C Bianco; Andrew J Bauer; Kenneth D Burman; Anne R Cappola; Francesco S Celi; David S Cooper; Brian W Kim; Robin P Peeters; M Sara Rosenthal; Anna M Sawka Journal: Thyroid Date: 2014-12 Impact factor: 6.568
Authors: S Hüser; S Guth; H G Joost; S T Soukup; J Köhrle; L Kreienbrock; P Diel; D W Lachenmeier; G Eisenbrand; G Vollmer; U Nöthlings; D Marko; A Mally; T Grune; L Lehmann; P Steinberg; S E Kulling Journal: Arch Toxicol Date: 2018-08-21 Impact factor: 5.153
Authors: Rita S Strakovsky; Stéphane Lezmi; Jodi A Flaws; Susan L Schantz; Yuan-Xiang Pan; William G Helferich Journal: Toxicol Sci Date: 2013-12-21 Impact factor: 4.849
Authors: Serena Tonstad; Karen Jaceldo-Siegl; Mark Messina; Ella Haddad; Gary E Fraser Journal: Public Health Nutr Date: 2015-10-09 Impact factor: 4.022