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Soy isoflavones inducing overt hypothyroidism in a patient with chronic lymphocytic thyroiditis: a case report

  • Yuya Nakamura1, 2,
  • Isao Ohsawa1Email author,
  • Yoshikazu Goto1,
  • Mayumi Tsuji2,
  • Tatsunori Oguchi2,
  • Naoki Sato2,
  • Yuji Kiuchi2,
  • Motonori Fukumura3,
  • Masahiro Inagaki4 and
  • Hiromichi Gotoh1
Journal of Medical Case Reports201711:253

https://doi.org/10.1186/s13256-017-1418-9

Received: 17 May 2017

Accepted: 4 August 2017

Published: 5 September 2017

Abstract

Background

Many people have thyroid conditions that make them susceptible to hypothyroidism. If the foods they eat may interfere with the production of thyroid hormone, which can lead to development of serious hypothyroidism. The danger of health drinks should always be noted.

Case presentation

A 72-year-old Japanese woman was previously diagnosed with chronic lymphocytic thyroiditis caused by a goiter and had an elevated thyroid-stimulating hormone level (6.56 μIU/ml), a high anti-thyroid peroxidase antibody level (>600 IU/ml), and a high antithyroglobulin level (> 4000 IU/ml) but normal levels of free triiodothyronine (3.08 pg/ml) and thyroxine (1.18 ng/ml). She presented to our hospital with sudden-onset general malaise, edema, and hoarseness with an elevated thyroid-stimulating hormone (373.3 μIU/ml) level and very low triiodothyronine (< 0.26 pg/ml) and thyroxine (0.10 ng/ml) levels. It was determined that for 6 months she had been consuming a processed, solved health drink (“barley young leaf”) in amounts of 9 g/day, which included soybean and kale powder extract. Hypothyroidism might be affected by ingredients of health drinks. She discontinued consumption of the health drink immediately and began taking 12.5 μg of levothyroxine. The amount of levothyroxine was gradually increased every 3 days up to 100 μg. At day 61, her thyroid-stimulating hormone level had decreased (6.12 μIU/ml), her free triiodothyronine (2.69 pg/ml) and thyroxine (1.56 ng/ml) levels had increased, and her general condition was improved. Among risky foods lowering thyroid function, some experimental studies have revealed that isoflavones reduce thyroid function. Therefore, we measured the presence of isoflavones in the patient’s frozen serum with thin-layer chromatography. After she discontinued consumption of the health drink, two components quickly disappeared, and the other three components gradually decreased. On the basis of developing solvent composition and a positive ferric chloride reaction in thin-layer chromatography experiment, the five ingredients that disappeared or decreased were highly suspected to be soy isoflavones.

Conclusions

This case emphasizes that consuming health drinks that include soy isoflavone powder extracts can lead to severe hypothyroidism.

Keywords

Isoflavones Soybean Barley young leaf kale Hypothyroidism Chronic lymphocytic thyroiditis Thin-layer chromatography

Background

Many people have thyroid conditions that make them susceptible to hypothyroidism. For example, 10% of a disease-free population was reported to have positive results for anti-thyroid peroxidase antibodies (TPOAb) or antithyroglobulin (anti-Tg) [1], indicating that many patients have potentially chronic lymphocytic thyroiditis. However, there are many exogenous foods influencing the thyroid. If the foods interfere with the production of thyroid hormone, they can cause serious hypothyroidism.

We report a case of a patient with severe hypothyroidism induced by consuming a health drink. To the best of our knowledge, there are almost no other reports of patients with severe hypothyroidism induced by isoflavone. The components of the substances suspected to be isoflavones disappeared or decreased along with the clinical impairment of our patient. To the best of our knowledge, this is the first report of the presence of isoflavone in the serum of a patient with severe hypothyroidism.

Case presentation

A 72-year-old Japanese woman had been followed because of chronic lymphocytic thyroiditis caused by a goiter. She had an elevated thyroid-stimulating hormone (TSH) level (6.56 μIU/ml), a high TPOAb level (> 600 IU/ml), and a high anti-Tg level (> 4000 IU/ml) but normal levels of free triiodothyronine (T3; 3.08 pg/ml) and thyroxine (T4; 1.18 ng/ml). Her past medical history included only hypertension. She did not have any fever or neck pain suggestive of subacute or painless thyroiditis during recent months, and she had not taken any medication that would reduce thyroid function. Her social, family, and environmental histories were also unrevealing.

The patient had been taking a processed, solved health drink (“barley young leaf”) in amounts of 9 g/day, which included soybean and kale powder extract, for 6 months. She had gradually developed general malaise, edema, and hoarseness. She presented to our hospital with sudden-onset elevated TSH (373.3 μIU/ml) level and very low T3 (< 0.26 pg/ml) and T4 (0.10 ng/ml) levels. Her levels of total cholesterol, triglyceride, lactate dehydrogenase, aspartate transaminase, creatine phosphokinase, and immunoglobulin G were increased. These laboratory findings are shown in Table 1. Her goiter was swollen with mild hardness; her blood pressure at admission was 123/77 mmHg; her body temperature was 36.0 °C; and her pulse rate was 55 beats/minute. Computed tomography (Fig. 1) and thyroid ultrasound revealed bilateral thyroid enlargement. In addition, her uptake rate of 99mTc-pertechnetate was reduced. On the basis of these findings, we diagnosed severe hypothyroidism affected by ingredients of the health drink. She discontinued consumption of the health drink immediately and began taking 12.5 μg of levothyroxine. The amount of levothyroxine was gradually increased every 3 days up to 100 μg. After oral administration of levothyroxine, her high TSH levels decreased gradually, and her low free T3 and T4 levels increased. Her swelling and hoarseness disappeared, and her general condition improved. Her free T3 and T4 levels did not decrease in the follow-up period of the subsequent 6 months. The time line of this patient’s clinical course is shown in Fig. 2. Her TSH, free T3, and T4 levels are shown in Table 2.
Table 1

Patient’s laboratory findings on admission

 

Values

Normal ranges

Blood chemistry

Values

Normal ranges

Blood cell counts

 WBC, n/μl

57×102

40–90×102

TP, g/dl

8.3

6.7–8.3

 RBC, n/μl

389×104

380–480×104

Alb, g/dl

4.0

3.9–4.9

 Hb, g/dl

11.3

12.0–15.2

BUN, mg/dl

13.2

8.0–22.0

 Hct, %

36.0

35–48

Cr, mg/dl

1.0

0.4–0.7

 Plt, n/μl

13.1×104

14–34×104

UA, mg/dl

4.9

3.0–5.5

   

Na+, mEq/L

141

135–147

Serological tests

  

K+, mEq/L

3.5

3.5–5.0

 Fe, μg/dl

58

43–172

Cl, mEq/L

102

98–108

 UIBC, μg/dl

213

137–325

Ca2+, mg/dl

9.2

8.8–10.2

 TIBC, μg/dl

271

251–398

Pi, mg/dl

3.2

2.5–4.5

 Ferritin, ng/ml

72.8

5–157

AST, U/L

41

13–33

 IgG, mg/dl

2231

1156

ALT, U/L

28

6–27

 IgA, mg/dl

397

103

γ-GTP, U/L

31

10–47

 IgM, mg/dl

128

125

ALP, U/L

208

115–359

 NT-proBNP, pg/ml

49

< 125

LDH, U/L

330

119–229

   

T-Bil, mg/dl

0.6

0.2–1.2

Urinalysis

  

CPK, U/L

567

45–163

 Protein

T-chol, mg/dl

310

130–220

 Occult blood test

TG, mg/dl

233

30–150

   

HDL-chol, mg/dl

54

41.5–67.3

Fecal occult blood test

LDL-chol, mg/dl

187

70–139

   

Glu, mg/dl

85

70–110

   

CRP, mg/dl

0.15

< 0.30

Abbreviations: Alb Albumin, ALP Alkaline phosphatase, ALT Alanine transaminase, AST Aspartate transaminase, BUN Blood urea nitrogen, Ca 2+ Calcium, Cl Chloride, CPK Creatine phosphokinase, Cr Creatinine, CRP C-reactive protein, Fe Iron, γ-GTP γ-Glutamyltransferase, Glu Glucose, Hb Hemoglobin, Hct Hematocrit, HDL-chol High-density lipoprotein cholesterol, IgA Immunoglobulin A, IgG Immunoglobulin G, IgM Immunoglobulin M, K + Potassium, LDH Lactate dehydrogenase, LDL-chol Low-density lipoprotein cholesterol, Na + Sodium, NT-proBNP N-terminal pro-brain natriuretic peptide, Pi Inorganic phosphate, Plt Blood platelets, RBC Red blood cells, T-Bil Total bilirubin, T-chol Total cholesterol, T-chol Total cholesterol, TG Triglyceride, TIBC Total iron-binding capacity, TP Total protein, TSAT Transferrin saturation, UA Uric acid, UIBC Unsaturated iron-binding capacity, WBC White blood cell

Fig. 1

Computed tomographic scan showing thyroid enlargement (arrowheads)

Fig. 2

Timeline

Table 2

Patient’s clinical course based on laboratory findings after discharge

 

Before treatment

Day 11

Day 33

Day 61

Day 102

Normal range

TSH, μIU/ml

373.7

341.3

40.66

6.12

11.68

0.50–5.00

fT3, pg/ml

< 0.26

0.55

2.47

2.69

2.58

2.30–4.00

fT4, ng ml

0.1

0.28

1.41

1.56

1.45

0.90–1.70

Abbreviations: fT3 Free triiodothyronine, fT4 Thyroxine, TSH Thyroid-stimulating hormone

There are many risky foods lowering thyroid function, such as soybean and cruciferous vegetables, especially in a patient with chronic lymphocytic thyroiditis. Among these foods, some experimental studies have shown that isoflavone reduces thyroid function [2, 3]. It was suspected that isoflavones might be the reason for our patient’s hypothyroidism. Therefore, we measured the presence of isoflavone in the patient’s frozen serum at 5 points from before admission to day 102 for further investigation. A blood sample was pretreated as described previously [4]. The sample was analyzed with thin-layer chromatography on precoated silica gel 60 F254 or RP-18 WF254 plates (Merck Millipore Corporation, Darmstadt, Germany), with detection achieved by spraying with iron(III) chloride solution. After she discontinued consuming the health drink, two components quickly disappeared, and the other three components gradually decreased (Fig. 3). On the basis of developing solvent composition and a positive ferric chloride reaction in thin-layer chromatography experiment, the five ingredients that disappeared or decreased were highly suspected to be soy isoflavones.
Fig. 3

Results of the thin-layer chromatography. After discontinuing health drink, two components (arrow heads) quickly disappeared and the other three components (arrows) gradually decreased. From the composition of the developing solvent and the positive findings of ferric chloride, these ingredients were speculated highly likely for soy isoflavone

Discussion

Isoflavone, one of the isoflavonoids, is associated with breast cancer, prostate cancer, cerebral infarction, and myocardial infarction [57]. Moreover, some researchers have reported that soy isoflavone might reduce thyroid function by suppressing thyroid peroxidase [2, 3]. In our patient, the components of the substances suspected to be isoflavones had disappeared or decreased along with her clinical impairment. To the best of our knowledge, this is the first case report in which the presence of isoflavone has been examined in the serum of a patient with severe hypothyroidism. This point is unique; to the best of our knowledge, there have been almost no other reports in which the presence of isoflavone has been examined in patient serum. The other following two mechanisms of hypothyroidism by soybean are considered: (1) An alcohol-soluble component in soybean inhibits iodide uptake [8], and (2) phytic acid salt in soybean chelates the essential minerals, especially zinc, for thyroid hormone production [9, 10]. Our patient presented with severe hypothyroidism after 6 months of regular consumption of a health drink. Because the thyroid contains several months’ storage of thyroid hormone [11], overt hypothyroidism might present late. It is necessary to investigate further the detailed mechanisms of hypothyroidism caused by soy isoflavones.

Conclusions

This case emphasizes that consuming health drinks that include soy isoflavone powder extract can lead to severe hypothyroidism.

Declarations

Acknowledgements

Not applicable.

Funding

None.

Availability of data and materials

All data generated or analyzed for this report are included in this published article.

Authors’ contributions

YN, IO, MF, and MI conceived of and designed the laboratory measurements​. YN, IO, MF, and MI analyzed the data. YN wrote the first draft of the manuscript. IO critically revised the manuscript. YG, MT, TO, NS, YK, and HG jointly developed the structure and arguments for the paper. IO and YK made critical revisions and approved the final version of the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

Competing interests

The authors declare that they have no competing interests.

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Authors’ Affiliations

(1)
Department of Internal Medicine, Saiyu Soka Hospital
(2)
Department of Pharmacology, School of Medicine, Showa University
(3)
Division of Natural Medicine and Therapeutics, Department of Clinical Pharmacy, School of Pharmacy, Showa University
(4)
Department of Chemistry, College of Arts and Sciences, Showa University

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Copyright

© The Author(s). 2017

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