Iodine deficiency is the most common cause of hypothyroidism. Iodine is essential for the healthy function of the thyroid gland and adequate amounts must be obtained from the diet or its function is inhibited. A chronic deficiency of iodine may produce goitre.¹

The presence of iodine in our diet is dependent on the concentration of this mineral in the soil. This affects the pasture and animals grazing on it, as well as crops such as vegetables and fruit. Water also contains iodine in areas where it has leached from the surrounding rocks and soil; however, iodine is generally deficient in the Australian inland environment.

Dietary iodine is also consumed bound to amino acids, and the iodine-based hormones thyroxine (T4) and triiodothyronine (T3) are examples of this. These hormones are absorbed unchanged, meaning that they can also be administered as medicine for treating thyroid conditions.

After absorption iodine travels to all the tissues, in particular the thyroid gland which makes the hormones T3 and T4. The gland traps iodine at about 60 mg daily and contains 80% of the body’s iodine. Several organs of the body including the liver and kidneys can synthesise T3 from T4 if there are other adequate nutrients in the diet (tyrosine, selenium, zinc, vitamins A, B, C, D, E), indicating the crucial role of these cofactors in iodine metabolism.

T3 and T4 bind to receptors in the cell nucleus, thereby affecting gene expression and subsequent down-stream protein synthesis. T4 is converted to T3, with T3 being more potent but shorter lived than T4. The influence on metabolism of these hormones is general: they stimulate the basal metabolic rate, oxygen consumption, heat production and growth.²

The type of goitre produced in iodine deficiency is usually a diffuse non-inflammatory swelling of the whole gland, stimulated by elevated thyroid stimulating hormone (TSH), which is a response to low serum levels of thyroid hormones (T3 and T4). The gland cannot synthesize these hormones due to inadequate nutrient supply and compensates by growing in size in order to trap more iodine. The gland becomes palpable at the front of the neck, and the usual accompanying symptoms are cold intolerance, fatigue, constipation, reduced heart rate, weight-gain and depression.

Other possible causes of goitre are autoimmune inflammatory conditions such as Hashimoto’s thyroiditis and Grave’s disease. In Hashimoto’s thyroiditis the gland becomes inflamed due to an autoimmune attack, enlarging and becoming less active due to lymphocyte infiltration and fibrosis. The result is that the patient becomes hypothyroid with the same symptoms as iodine deficiency. There are also antibodies present on testing (thyroid peroxidase, thyroglobulin, TSH receptors). Interestingly, Hashimoto’s is also associated with excess iodine intake.

In Grave’s disease the inflammation is also due to an autoimmune response to the TSH receptor, but in this case the thyroid is stimulated to produce excess T3 and T4, resulting in characteristic hyperthyroid symptoms. The pituitary responds by decreasing TSH, as is evident on tests, but T3 and T4 remain high. The symptoms are mostly opposite those mentioned above for hypothyroid: fatigue, fast heart rate, palpitations, heat intolerance, weight-loss, loose bowel, sweatiness and anxiety.

It is important to have a regular intake of iodine because the body does not store it. Foods rich in iodine are sea vegetables (nori, kombu, dulse, wakame), ocean fish, shrimp, oysters, sea salt and iodised salt. Limited amounts are found in spinach, egg, sunflower seed, mushroom, asparagus, potatoes, as well as dairy (due to sterilisation of equipment with iodine). Vegans are particularly prone to iodine and selenium deficiency.³ Pregnancy also increases iodine dietary requirement by 50%.

Unfortunately, the consumption of some foods called goitrogens inhibits iodine absorption by binding to dietary iodine (soy, cassava, broccoli, cabbage, kale, turnips, peanuts). Cooking generally reduces this effect. Fluoride also inhibits iodine uptake.⁴

Kelp tincture, also bladderwrack (Fucus vesiculosus), is ideal for correcting a deficiency of Iodine. Superior to mineral iodine drops, kelp is a tonic to the glandular system and contains other important cofactors for thyroid hormone synthesis. It is rich in iodine, magnesium, potassium, calcium, sulphur, iron, zinc and copper, and has good levels of important vitamins (A, B2, B12, C, D, E, K). Importantly, excess use of iodine drops can also cause thyroid dysfunction.^1,5,6

Disclaimer: this article is intended for the purpose of general education only, and is not a substitute for a diagnosis, treatment advice, or a prescription given in a consultation with a qualified physician.

References:

1.         Stuss M, Michalska-Kasiczak M, Sewerynek E. The role of selenium in thyroid gland pathophysiology. Endokrynol Pol 2017;68:440–65.

2.         Gropper, Smith, Groff. Advanced Nutrition And Human Metabolism. 5th ed. Wadsworth: Cengage Learning; 2009.

3.         Fallon N, Dillon SA. Low Intakes of Iodine and Selenium Amongst Vegan and Vegetarian Women Highlight a Potential Nutritional Vulnerability. Front Nutr 2020;7:72.

4.         Waugh DT. Fluoride Exposure Induces Inhibition of Sodium-and Potassium-Activated Adenosine Triphosphatase (Na+, K+-ATPase) Enzyme Activity: Molecular Mechanisms and Implications for Public Health. Int J Environ Res Public Health 2019;16.

5.         Catarino MD, Silva AMS, Cardoso SM. Phycochemical Constituents and Biological Activities of Fucus spp. Mar Drugs 2018;16.

6.         Boericke W. Pocket Manual Of Homoeopathic Materia Medica, c. 1927. Delhi: Indian Books & Periodical Publishers; 2007.