Home > For Health Professionals > Education and Prevention > Food

Food

Fact sheet: Review of cases with unexplained thyroid dysfunction: Information for Medical Practitioners, Endocrinologists and Chief Health Officers

A cluster of cases diagnosed with thyroid conditions is believed to be associated with the consumption of seaweed and products containing seaweed. Information for Medical Practitioners, Endocrinologists and Chief Health Officers is now available.

PDF printable version of Review of cases with unexplained thyroid dysfunction: Information for Medical Practitioners, Endocrinologists and Chief Health Officers (PDF 76 KB)

Review of cases with unexplained thyroid dysfunction: Information for Medical Practitioners, Endocrinologists and Chief Health Officers

5 Key points for Medical Practitioners, Endocrinologists and Chief Health Officers

1. A cluster of cases diagnosed with thyroid conditions is believed to be associated with the consumption of seaweed and products containing seaweed, including the now recalled products BonSoy soy milk and Heng Fei Brand Dried Seaweed.
2. Doctors should review recent cases of unexplained thyroid dysfunction and seek information about their consumption of seaweed and products containing seaweed.
3. Doctors should be alert to seek information about consumption of seaweed and products containing seaweed by any persons presenting with thyroid conditions.
4. Suspected cases should be reported to local public health authorities.
5. Some examples of products that contain seaweed are sushi, miso soup and various snacks.

BonSoy is a soy milk product that was distributed nationally in Australia. BonSoy soy milk has been withdrawn from the marketplace following detection of extremely high levels of iodine in added seaweed extract. Consumption of BonSoy soy milk has been linked to clinical thyrotoxicosis and, less commonly, hypothyroidism. Iodine crosses the placenta and may cause foetal and neonatal hypothyroidism which can cause developmental problems in the newborn.

A dried seaweed product has also now been found to have high levels of iodine and has been recalled from the market place.

Recommended levels of iodine

The recommended daily intake for iodine depends on age and life stage:

• Younger children (1 to 8 years) – 90µg
• Older children (9 to 13 years, boys and girls) – 120µg
• Adolescents (14 to 18 years) – 150µg
• Men – 150µg
• Women – 150µg v
• Pregnancy and breastfeeding – 220µg and 270µg respectively.

The recommended safe upper limit for iodine is:

• Young children (1 to 3 years) – 200µg
• Older children and Adolescents (14 years) – 900µg
• Adults – 1,100µg

Signs and Symptoms excessive iodine intake

Excessive iodine can lead to hyperthyroidism or, less commonly in adults, hypothyroidism. Infants appear more susceptible to hypothyroidism following excessive iodine exposure. The most common symptoms of hyperthyroidism are palpitations, fatigue and weight loss. Hypothyroidism is often insidious and, in mild cases, may only be detected on routine screening but it can cause fatigue, weight gain and mental clouding.
Top of Page

Medical Management

• Patients should be advised not to consume the product and to dispose of it either down the drain or in the garbage bin.
• Iodine has a half life of approximately 30 days.
• When a patient presents with a history of prolonged consumption of seaweed products, such as BonSoy soy milk, together with symptoms or signs listed above, Medical Practitioners should consider measurement of TSH. If the TSH is abnormal, proceed to measurement of the urinary iodine level (normal range in children 100-500 ug/L) and thyroid antibodies and consider referral to an endocrinologist or at least try to obtain phone consultation with an endocrinologist. There is no need to measure the urinary iodine level if the TSH is normal (Normal range 0.3-4.0 mU/L, can vary between laboratories) as stopping the ingestion of the seaweed product will return the body’s iodine levels to normal within a few weeks.
• Advice to patients who report they have consumed a seaweed product and are pregnant: see your GP or obstetrician for a TSH measurement. The newborn baby is at risk for Transient Hypothyroidism and should have a TSH and free T4 measurement done soon after birth (this is usually routinely done with the Guthrie heelprick test); and again at 14 days of age. If the TSH is abnormal at birth, then treatment and further tests may be required – these should be conducted under endocrinologist supervision. The effect of the high iodine levels will be to block synthesis of thyroid hormones causing hypothyroidism which in the neonatal period could cause a permanent loss of cognitive function.

Report suspected cases of excessive iodine consumption

Suspected cases of excessive iodine consumption should be reported to local public health authorities (public health unit or health department). Products that contain seaweed include sushi, miso soup and various snacks.

Where possible, an estimation of the amount of seaweed or product containing seaweed that was consumed by the patient should be provided to the local public health authority.

Further information

For further information, please contact your local public health authority or email the Department of Health and Ageing at OzFoodNet@health.gov.au.

Advice for the general public about product recalls and information about iodine are available on the Food Standards Australia New Zealand website: http://www.foodstandards.gov.au/