Iodide

Iodide, urine, normalised to creatinine

U -Isuht. ATK 8014

Partial examinations:
U -I KL 1984
​U -Krea KL 2145

ATK 8228 Package study that includes all three values (ATK 8014, KL 1984, KL 2145)

Iodine serves as a foundational component of thyroid hormones, making it indispensable for normal growth, development, and metabolic processes. The majority of the body’s iodine content, which totals around 15-20 mg, is primarily situated within the thyroid gland, accounting for 70-80% of the total amount. Ensuring sufficient iodine intake is of particular significance during the fetal stage and the initial years of life, as thyroid hormones play a vital role in the development of the brain. In subsequent life stages, thyroid hormones not only regulate basic metabolism but also contribute to the body’s ability to adapt to prolonged periods of stress. Approximately 90% of the iodine present in the bloodstream is excreted through the kidneys into the urine, and the iodine concentration in the urine serves as an accurate indicator of the body’s iodine intake.

Indications

Assessment of sufficient iodine intake

Sample

5 – 10 mL of morning urine that has been in the bladder for 3 – 4 hours.

Collect 1 mL of morning urine that has been held in the bladder for a minimum of 4 hours but no longer than 12 hours. Fluctuations in fluid balance can compromise the reliability of the test outcomes. In the period leading up to the sample collection, it’s essential to steer clear of excessive fluid intake, fluid restriction, and intense physical exertion. Refrain from taking iodine-containing supplements for a 24-hour window before the collection. The presence of a small quantity of table salt does not impede the analysis. There should be a gap of over 3 months since any contrast agent examinations before the sample collection. To prevent contamination, it’s advised to cleanse the hands and the area around the urethral opening with water before collecting the sample. Ensure that blood and urine are not mixed during the collection process.

Storage and delivery

Delivery at room temperature on sampling day (Mon-Wed). Can be stored refrigerated over the weekend. Store frozen when longer, ship frozen sample frozen.

Method

Iodine assay: ICP-MS. The result is normalised to creatinine value (U -Krea, photometric) measured from the same urine sample.

Turnaround time 

10 weekdays

Reference ranges 

Reference values recommended by the WHO for the U-I study:

Asults and children over 6 years old:

During pregnancy:

less than 150 µg/L deficient iodine intake
150 – 249 µg/L adequate iodine intake
250 – 499 µg/L iodine intake exceeding the requirements
≥ 500 µg/L excessive iodine intake

Breastfeeding mothers and children under 2 years old:

less than 100 µg/L deficient iodine intake
≥ 100 µg/L adequate iodine intake

In breastfeeding mothers and children under 2 years of age, a urinary iodide (U -I) concentration of 100 µg/L can be considered the limit of adequate iodine intake, but no other recommended values have been defined for these groups.

Iodine guidelines by WHO: World Health Organization. United Nations Children’s Fund & International Council for the Control of Iodine Deficiency Disorders. Assessment of iodine deficiency disorders and monitoring their elimination. 3rd ed. Geneva, Switzerland: WHO, 2007

Reference areas of the U -Krea study:

women 1.7 – 19.4 mmol/L
​men 2.3 – 23.5 mmol/L

Based on HUSLAB material.

Interpretation of results

The recommended iodine intake for adults is 150 µg/day. Iodine is solely obtained from dietary sources, a factor closely influenced by the iodine content in soil and food processing methods. Principal iodine-rich foods encompass dairy products, cereal products, iodized table salt, fish, shellfish, and algae. However, the presence of goitrogens in certain foods and cigarette smoke can obstruct iodine’s accessibility to thyroid cells. Examples of goitrogenic foods include raw turnips, carrots, cabbage, spinach, sweet potatoes, pears, peaches, strawberries, peanuts, soy products, and even cooked millet. These foods become particularly noteworthy in the context of an existing iodine deficiency.

Iodine deficiency

Long-term and widespread iodine deficiency leads to thyroid dysfunction, potentially giving rise to developmental, growth, and essential functional disorders. The global issue of chronic iodine deficiency can be mitigated by timely diagnosis and intervention.

Iodine deficiency is also prevalent among Finns, especially those adhering to salt restrictions unless alternative sources of iodine are secured. Inadequate iodine intake during fetal development can result in miscarriage, fetal demise, and congenital anomalies. If left untreated, iodine deficiency contributes to cretinism and intellectual disability. In adulthood, iodine deficiency might manifest as an enlarged thyroid, reduced work efficiency, impaired cognitive functions, and could impact the likelihood of macular degeneration. Individuals following a vegan and dairy-free diet should be particularly vigilant about their iodine intake.

Assessing iodine status is essential for everyone, at least once. Often, when addressing hypothyroidism symptoms with medication, the underlying issue might actually be iodine deficiency. However, before initiating iodine treatment, it’s crucial to rule out any underlying thyroiditis, as the treatment approach should be more comprehensive in such cases.

Excessive iodine intake

Overconsumption of iodine poses a risk when using dietary supplements, dried seaweed, and potentially certain medications containing iodine. The maximum allowable daily iodine intake for adults is 600 µg. Depending on an individual’s iodine status, excessive intake can lead to either hypothyroidism or hyperthyroidism. During pregnancy, excessive iodine intake is hazardous, as it can induce hypothyroidism in newborns.

Self-administering iodine supplements out of concern for radiation danger can result in life-threatening situations.

References:

Iodine guidelines by WHO: World Health Organization. United Nations Children´s Fund & International Council for the Control of Iodine Deficiency Disorders. Assessment of iodine deficiency disorders and monitoring their elimination. 3rd ed. Geneva, Switzerland: WHO, 2007 

https://apps.who.int/iris/bitstream/handle/10665/43781/9789241595827_eng.pdf?sequence=1

https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/#h5

Inquiries

martin.tornudd@milalab.fi

Last update 8.8.2023