Effect of Excess Iodine on Oxidative Stress Markers, Steroidogenic-Enzyme Activities, Testicular Morphology, and Functions in Adult Male Rat

[helvella]

We see claims of every sort in relation to iodine intake. When people take high doses, they often claim to feel well on it and hope they are protecting themselves from some cancers. I hope that they both do feel well and are protecting themselves. This paper, however, suggests that the impact might be rather more complex, profound and with a level of feedback which enhances the impact - and not in a good way.

Biol Trace Elem Res. 2015 Dec 23. [Epub ahead of print]

Effect of Excess Iodine on Oxidative Stress Markers, Steroidogenic-Enzyme Activities, Testicular Morphology, and Functions in Adult Male Rats.

Chakraborty A1, Mandal J1, Mondal C1, Sinha S1, Chandra AK2.

Author information

1Endocrinology & Reproductive Physiology Laboratory, Department of Physiology, University of Calcutta, University College of Science and Technology, 92, Acharya Prafulla Chandra Road, Kolkata, 700 009, West Bengal, India.

2Endocrinology & Reproductive Physiology Laboratory, Department of Physiology, University of Calcutta, University College of Science and Technology, 92, Acharya Prafulla Chandra Road, Kolkata, 700 009, West Bengal, India. [e-mail].

Abstract

Improper iodine intake is a major concern in public health. Chronic intake of low iodine affects gonadal functions of man and animals; however, such effects of excess iodine in male reproduction, specially on testicular morphology, testicular steroidogenic enzyme activities, sperm morphology, sperm viability, and sperm count including male hormonal profiles in reference to iodine status and thyroid hormone profiles are yet to be explored. With this background, adult male rats of 120 ± 10 gm Bw of 90 ± 5 days were divided broadly in two groups depending on the duration of the treatment for 30 and 60 days, respectively. Both the groups consisted of control animals. Excess iodine (100EI), i.e., 100 times more than its recommended level but within its tolerable ranges, was administered through gavage regularly to the first group of experimental animals for 30 and 60 days, respectively, and excessive iodine (500EI), i.e., 500 times more than its recommended level and above tolerable range in the same way and for the same durations, was administered to the other group of experimental animals. Overall results revealed that regular consumption of iodine in excess impairs reproductive functions in adult male rats depending on the dose and duration of its exposure through different mechanisms. Excess iodine accumulates in the testis which results in generation of reactive oxygen species (ROS) as evidenced by higher lipid peroxidation level as well as an imbalance in the pro-/antioxidant status inhibiting the activity of ∆5 3β- hydroxysteroid dehydrogenase (HSD) and 17β-HSD resulting to reduced synthesis of testosterone that causes structural and functional changes of the testis. Secondly, persistent generation of ROS in testis as a result of prolonged excess iodine exposure affects hypothalamo-pituitary-adrenal axis that stimulates synthesis and secretion of corticosterone which inhibits LH release that downregulates testosterone synthesis causing further testicular disruption. Thirdly, excess iodine when administered above its tolerable ranges for prolonged duration acts on thyroid itself developing a state of biochemical hypothyroidism (as evident by low T3) which further potentiate the disrupting effect of excess iodine on male gonads by reducing circulating testosterone level.

KEYWORDS:

Corticosterone; Excessive iodine; Pro-/antioxidant status; Reactive oxygen species; Steroidogenic enzymes; Testosterone

PMID: 26701334 [PubMed - as supplied by publisher]

ncbi.nlm.nih.gov/pubmed/267...

[Hidden]

Unseen damage is very dangerous and I am guessing irreversible?

And I assume a similar damage could be instilled on the female reproductive system and hormones ? After all the ovaries have the second largest concentration of iodine in the body affecting ovarian production of estrogens and changes in the estrogen receptors.

We know the effect of iodine on the endocrine system but I have been reading about it positively aiding blood sugar problems by increasing sensitivity to insulin receptors and also helping polycystic ovarian syndrome (PCOS).

As iodine is crucial for the body to be able to achieve hormone balance it makes sense that too much or too little could also cause major disruption and anyone thinking of supplementation should do a loading test to assess levels.

Thank you for posting Helvella,

Flo

[helvella Administrator Thyroid UK in reply to Hidden]

The message I get from the scientific establishment is that the right level of iodine is critical. But changing from inadequate to sufficient iodine is something to be done carefully - not just diving in with high doses.

[greygoose in reply to helvella]

Been saying that for a long time!

[Arijit_Chak]

I have been the first author of the article and I say that too much iodine is not beneficial for health especially on reproductive organs which contains Na-I symporter.

[helvella Administrator Thyroid UK in reply to Arijit_Chak]

You are very welcome here. There are a few academics who contribute from time to time - like diogenes.

We keep seeing some people claiming that large doses of iodine are positively beneficial - often the name Dr Brownstein is quoted. I am very sceptical and, at the least, feel the need to suggest people read, read and read a bit more before making any decisions.