Beyond thyroid dysfunction: the systemic impact of iodine excess

Yet another paper which is highlighting the issues which can be caused by excess iodine intake.

In particular, read the Conclusion in the full paper.

Beyond thyroid dysfunction: the systemic impact of iodine excess
Aiman Khudair  1† Sara Anjum Niinuma 1† Haniya Habib 1† Butler 2*

    1 School of Medicine, Royal College of Surgeons in Ireland - Medical University of Bahrain, Busaiteen, Bahrain
    2 Research Department, Royal College of Surgeons in Ireland - Medical University of Bahrain, Busaiteen, Bahrain

As an essential micronutrient, iodine plays a crucial role in several physiological systems, particularly in the production of thyroid hormone. While deficiency is widely recognized, the consequences of iodine excess (IE) are less studied. IE, which may be caused by iodine-rich diets, supplements, iodinated contrast media and salt iodization, has been implicated in a range of adverse outcomes on thyroid and systemic health. Examples include autoimmune thyroid diseases like Graves’ disease and Hashimoto’s thyroiditis, driven by immune cell polarization and gut microbiota alterations. Furthermore, excessive iodine intake is associated with increased risks of cardiovascular diseases, including hypertension and atherosclerosis, due to oxidative stress, inflammation, and endothelial dysfunction. It contributes to the development of thyroid cancer, particularly papillary thyroid cancer, through genetic mutations such as BRAF mutations and enhanced cancer cell proliferation. Excess iodine intake has been implicated to have neurotoxic effects, significantly impairing learning and memory, negatively impacting neonatal brain development, and potentially contributing to the progression of neurodegenerative conditions. It also has a potential role in renal dysfunction in vulnerable populations, due to overload from povidone-iodine in sterile equipment. This mini-review aims to collate the adverse effects of IE, beyond its effect on thyroid health, through investigation of the cardiovascular, nervous, and renal systems. Through our consolidation of the current literature, we hope to raise awareness and contribute to the understanding of the multifaceted impact of excessive iodine intake.

Open access:

https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2025.1568807/full

In vitro efficacy of aqueous PVP-iodine solution below 5% as alternative to preoperative antisepsis in ophthalmology as the basis for an in vivo study

Good to see people questioning standard practice. Also good to see recognition of the potential for a thyroid issue - though they do not seem to see any thyroid issues with the 5% solution.

In vitro efficacy of aqueous PVP-iodine solution below 5% as alternative to preoperative antisepsis in ophthalmology as the basis for an in vivo study

Paula Zwicker, Nevin Opitz, Julia Harris, Andreas Stahl, Ulrich Kellner, Ruth Koelb-Keerl, Philipp S. Muether, Anne Hunold & Axel Kramer 

Abstract

Purpose

Pre-operative antisepsis of the conjunctiva is indicated prior to intraocular surgery to prevent post-interventional endophthalmitis. In Germany, antisepsis with 5% povidone-iodine (PI) aqueous solution is explicitly required prior to intravitreal injections (IVI), and also generally recommended for intraocular surgery. However, this concentration often leads to a foreign body sensation and an unpleasant burning in combination with dry eye symptoms. Postoperative eye pain, persistent corneal epithelial defects, and a risk of keratitis are further side effects. Due to the repetitive nature of IVI, these symptoms are particularly present in IVI patients. A reduced concentration may be favorable to decrease patient discomfort. A 1.25% PI solution does not increase the iodine concentration in the aqueous humor and is also used for prophylaxis of ophthalmia neonatorum and for preoperative antisepsis; in both cases the renal iodine excretion stays in a physiological range thus thyroid diseases are no contraindication for its use. Thus, the efficacy of reduced concentrations of PI should be evaluated in vitro.

Methods

PI with dilutions below 5% (0.625 − 2.5% serial 1:2 dilution) was tested in vitro in a quantitative suspension assay and in a quantitative carrier test without and with addition of matrices to identify their antimicrobial effect against Staphylococcus epidermidis, Pseudomonas aeruginosa, Cutibacterium acnes and Candida albicans.

Results

No differences in the antimicrobial effect was seen due to reduced concentrations of PI in comparison to a 5% solution. However, a trend was seen regarding the required contact time of the antiseptic solution.

Conclusion

The in-vitro tests have shown adequate antisepsis of 1.25% PI prior to intraocular surgery. However, it is important to pay attention to a sufficient contact time of the antiseptic of about 1 min before ophthalmologic intervention. In order to give final recommendations, in vivo testing is needed to build a robust data foundation.

Highlights

5% PVP-Iodine solution prior IVI leads to unpleasant side effects.

In vitro, antimicrobial effect of 5% PI is comparable to that of 1.25% PI.

Addition of matrices had no visible effects on antimicrobial activity.

Contact time of 1 min is necessary.

Unusually, an Open Access paper:

https://joii-journal.springeropen.com/articles/10.1186/s12348-025-00489-3