The effect of soy phytoestrogen supplementation on thyroid status and cardiovascular risk markers in patients with subclinical hypothyroidism

A randomized, double-blind, crossover study

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

Research output: Contribution to journalArticle

44 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)1442-1449
Number of pages8
JournalJournal of Clinical Endocrinology and Metabolism
Volume96
Issue number5
DOIs
Publication statusPublished - May 2011
Externally publishedYes

Fingerprint

Phytoestrogens
Hypothyroidism
Double-Blind Method
Cross-Over Studies
Thyroid Gland
Insulin Resistance
Blood Pressure
Blood pressure
C-Reactive Protein
Insulin
Soybean Proteins
Nutrition
Outcome Assessment (Health Care)
Vegetarian Diet
Lipids
Tertiary Healthcare
Dietary Supplements

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

Cite this

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.

In: Journal of Clinical Endocrinology and Metabolism, Vol. 96, No. 5, 05.2011, p. 1442-1449.

Research output: Contribution to journalArticle

Sathyapalan, Thozhukat ; Manuchehri, Alireza M. ; Thatcher, Natalie J. ; Rigby, Alan S. ; Chapman, Tom ; Kilpatrick, Eric S. ; Atkin, Stephen. / The effect of soy phytoestrogen supplementation on thyroid status and cardiovascular risk markers in patients with subclinical hypothyroidism : A randomized, double-blind, crossover study. In: Journal of Clinical Endocrinology and Metabolism. 2011 ; Vol. 96, No. 5. pp. 1442-1449.
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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.",
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