See also Iodine Post 1 and Iodine Post 2.
Females: Pre-conception, conception and iodine
Bottom Line: I could find nothing concrete that convinced me that intake of iodine beyond commonly recommended doses improved the occurrence of conception, the regularity of periods, ovulation patterns, or menstruation abnormalities per se. However, without enough iodine, we are brought back to the fact that hypothyroidism can develop, and hypothyroidism can cause these fertility alterations. So females DO need to be getting enough iodine from somewhere and/or eliminating environmental factors that can affect iodine’s use in the body (a later post).
I easily found research supporting hypothyroidism (low thyroid function with symptoms and clear-cut lab abnormalities) and subclinical hypothyroidism’s (lab values not clear cut and patient not all-out symptomatic) roles in issues leading to conception, with both disorders affecting levels of sex hormones, ovulation patterns, menstrual patterns, and the ability to conceive even with the occurrence of ovulation.
- In the International Journal of Applied and Basic Medical Research (2012), of 394 infertile women, 23.9% were found to be hypothyroid (TSH > 4.2 μIU/ml). After treatment with thyroid hormone (thyroxine) for hypothyroidism, 76.6% of infertile women conceived within 6 weeks to 1 year. Recommendations in the article boiled down to this: “Thyroid evaluation should be done in any woman who wants to get pregnant with [a] family history of thyroid problem or irregular menstrual cycle or had more than two miscarriages or is unable to conceive after 1 year of unprotected intercourse. The comprehensive thyroid evaluation should include T3 , T4 , thyroid stimulating hormone (TSH), and thyroid autoimmune testing such as thyroid peroxidase (TPO) antibodies, thyroglobin/antithyroglobin antibodies, and thyroid stimulating immunoglobulin (TSI). Thyroid autoimmune testing may or may not be included in the basic fertility workup because the presence of thyroid antibodies doubles the risk of recurrent miscarriages in women with otherwise normal thyroid function.” (1)
- From Human Reproduction, 2003, a follow–up study on infertility found that never achieving a TSH <2.5 with thyroid replacement medication resulted in lower conception rates. (2) I find this interesting because lots of women with a TSH in the normal range (0.5-5) are told their “thyroids are fine,” and yet this study indicates optimal fertility occurs with a TSH< 2.5! So if 2.5 is optimum, I know a lot of women aren’t at this level.
Well, we’ve digressed to hypothyroidism rather than iodine! Hypothyroidism can be caused by iodine deficiency because iodine is essential for making thyroid hormone, but we are taught as medical doctors that hypothyroidism in the United States and developing countries is not due to iodine deficiency–although how we would know for absolute I can’t say. I NEVER once ordered or saw tests ordered for iodine levels. So I wonder about the iodine status in the patients in these and other studies. Could they have had lower levels of iodine contributing to their hypothyroidism? We have to have suspicion of iodine deficiency to diagnose it, and if we miss it, we’ve stuck a patient on thyroid hormone replacement probably for life.
From The American Thyroid Association website (phrases bolded by me):
“As iodine levels fall, hypothyroidism may develop, since iodine is essential for making thyroid hormone. While this is uncommon in the United States, iodine deficiency is the most common cause of hypothyroidism worldwide… How is iodine deficiency treated? There are no tests to confirm if you have enough iodine in your body. When iodine deficiency is seen in an entire population, it is best managed by ensuring that common foods that people eat contain sufficient levels of iodine. (3)”
I think this is a little backwards. We check for iodine deficiency as a population, knowing that some of the population will fall outside the realm of sufficiency, and then we have the balls to look people in the eye as individuals and say, “Your hypothyroidism is not caused by iodine deficiency.” I am not saying it is or it isn’t! I’m saying, based on my reading, WE DON’T KNOW! Neither are we educating doctors to have suspicion! On the other hand, many iodine-promoting websites tout iodine as a cure for things like infertility and menstrual abnormalities. I don’t think this is fair, either, since aside from its connection to hypothyroidism (which is not always due to low iodine), there isn’t much documentation to support this.
However, I did find some animal studies to look at regarding iodine and female fertility (I know animal studies shouldn’t be used as a substitute for human studies, but we don’t have those available.):
- Increased fertility in sheep: One study looked at mating ewes and rams in an iodine deficient area. One group of ewes and rams received iodine injections, and the control group did not. The study showed that 100% of the treated ewes mated with treated rams were pregnant versus only 37% of the control ewes mated with control rams. (I don’t know the breakdown of events, perhaps the untreated ewes and rams conceived 100% of the time too, but the ewes had miscarriages later. Iodine sufficiency is shown to decrease miscarriages, which will be covered in the next post.) (4)
- Increased fertility in horses: Reportedly, a Russian study (Kruzkova, 1968) indicated that mares which had shown anovulatory cycles responded to iodine supplementation. (5)
- Decreased fertility in chickens: In chickens, increasing iodine actually DECREASED some of the fertility markers, such as egg production and follicle production without ovulation, and normal fertility returned after iodine supplementation removal. Normal egg production returned after removal of iodine. (6)
Overall, improved fertility prior to conception seems to be related to iodine’s relationship to the production of thyroid hormone. Both too much iodine and too little iodine may be a problem (although there are questions out there about if iodine is accompanied by certain co-factors will this alleviate the problems know to be associated with iodine repletion/supplementation) and affect fertility.
But what about men? What does iodine have to do with their virility?
We can again see, as in female fertility, that HYPOTHYROIDISM plays a strong role:
- Thyroid hormone is important to help the Sertoli cells in the seminiferous tubules of the testes make sperm (spermatogenesis).
- Hyperthyroidism and hypothyroidism have been shown to affect the release of sex hormones from the pituitary in some studies (although not all studies).
- If hypothyroid, males can have an increase of prolactin levels, affecting libido, hypogonadism, erectile dysfunction, gynecomastia, and galactorrhea.
- Hypothyroidism also brings about decreases in testosterone and other male hormones.
- Young males who have hypothyroidism during the congenital period and early childhood period present reproductive issues later in life. Please note: The fact that hypothyroidism during the congenital period affects the male offspring’s reproduction is very important to remember. What a mother eats (or doesn’t eat) during pregnancy has lasting consequences on the fetus.
- Hypothyroidism, if prolonged, before puberty, can cause increased testicular size due to effects on the Leydig and Sertoli cells. These cells will increase in number but decrease in their maturity. There is a resultant drop in mature germ cells (sperm). (7)
Here again, these stated above results are for hypothyroidism–not iodine.
What about iodine deficiency and its supplementation’s effects on male fertility? In the Japanese Journal of Veterinary Research (2004) a statistical analysis explored whether the institution of iodine supplementation (such as in iodized salt in the 1920s in the US) could be responsible for the decline in sperm counts which affect developed nations such as the US. Through a complicated series of deductions and statistical analysis, these researchers felt that iodine supplementation WAS responsible for decreasing sperm counts. However, fascinatingly enough, it was noted that regions with perpetually high iodine intakes (Toulouse France on the Mediterranean Sea and Japan) have not experienced any decline in sperm counts. (8) [Please note that later in my reading, I saw that Toulouse, France had increasing occurrence of iodine deficiency in pregnant women. (9) ]
What questions does this raise? Are iodine saturated societies (such as Japan) protected from the decreasing sperm counts that seem to be seen elsewhere? In mild hypothyroidism from iodine deficiency, does the body then increase the cells which produce sperm to try to preserve reproduction, yet produce more immature sperm cells? Could there be something else besides iodine supplementation that decreases the sperm count? Clearly, there are a lot of factors introduced at the time which could decrease in sperm count.
Playing devil’s advocate in a weak fashion, the mentioned study concluded that sperm counts dropped significantly between 1965 and 1969 and attributes it to iodine supplementation. Another theory about the sperm fall revolves around hormone disruptors in the environment. What else was introduced and was all the rage about this time in America and Europe? Tupperware. Plastic. Potential hormone disruptor increasing estrogen-like effects in the body, and not just the BPA plastics, either. (10) So I will tuck this iodine and low sperm count thought away until perhaps more research comes along.
In animal studies: We can also take a look at an animal study specific to IODINE, rather than hypothyroidism. It has been found that administration of iodine to bulls improved the ejaculate volume and that in regions where iodine deficiency occurs, bulls’ fertility is affected due to decreased libido, ejaculate volume, sperm motility, and sperm cell concentration; supplementing iodine to these bulls improved the libido, ejaculate volume, sperm motility, and sperm cell concentration. (11)
So where are we left off? Hypothyroidism affects male fertility. Yes. Iodine supplementation we just don’t know about. A statistical analysis stretched and said iodine supplementation decreases sperm counts. An animal study showed benefits of iodine in bull fertility. What really happens in human males? I don’t feel there is enough out there for me to decide. If you speculate that iodine may improve the synthesis of thyroid hormone and perhaps help reverse hypothyroidism, then you can arrive at the conclusion that mild iodine deficiency in a male may decrease male fertility. There are other micronutrients (such as zinc and selenium) besides iodine that can affect sperm counts and male fertility, and perhaps these are all needed more as a person is iodine repleted to make sure there are no (or at least, less) adverse effects from the iodine supplementation. Don’t know. Wish I could deduce more.
So what did I decide about all those internet claims about improving male and female fertility with iodine? I think if iodine deficiency is causing a hypothyroid state, which may be overlooked by the medical community, then improving the thyroid function with iodine supplementation (and appropriate co-nutrients) could improve the chances to conceive. I don’t think I can safely assume and write more than that right now. In the next post, I will describe iodine effects in pregnancy. In the sense that iodine sufficiency helps cut down on miscarriages and stillbirths, it is true to say that iodine improves post-conceptual fertility. Pre-conceptual and conceptual fertility in males and females, I just haven’t decided.
1. Verma I, Sood R, Juneja S, Kaur S. Prevalence of hypothyroidism in infertile women and evaluation of response of treatment for hypothyroidism on infertility. Int J App Basic Med Res 2012;2:17-9. (http://www.ijabmr.org/article.asp?issn=2229-516X;year=2012;volume=2;issue=1;spage=17;epage=19;aulast=Verma)
2. Thyroxine treatment modified in infertile women according to thyroxine‐releasing hormone testing: 5 year follow‐up of 283 women referred after exclusion of absolute causes of infertility. Raber W, Nowotny P, et al. Hum. Reprod. (2003) 18 (4): 707-714. (http://humrep.oxfordjournals.org/content/18/4/707.long)
3. American Thyroid Association website: Iodine Deficiency. June 4, 2012. (http://www.thyroid.org/iodine-deficiency/)
4. Iodine supplementation restores fertility of sheep exposed to iodine deficiency. Ferri N, Ulisse S, et al. Journal of Endocrinological Investigation. November 2003, Volume 26, Issue 11, pp 1081-1087. (http://link.springer.com/article/10.1007/BF03345254#page-1)
5. Iodine in the horse: too much or too little. ( http://www.4source.com/technical/iodine1.shtml) (Could not find the actual abstract or article referred to.)
6. Effects of Excess Dietary Iodine upon Pullets and Laying Hens. Arrington, Santa Cruz, et al. The Journal of Nutrition. February 1967. 325-330. (http://jn.nutrition.org/content/92/3/325.full.pdf)
7. Thyroid Hormones in Male Reproduction and Fertility. Rajender Singh, Alaa J Hamadaand Ashok Agarwal. The Open Reproductive Science Journal. 2011. 3; 98-104.(https://www.clevelandclinic.org/reproductiveresearchcenter/docs/agradoc414.pdf)
8. Iodine intake as a possible cause of discontinuous decline in sperm counts: Ar e-evaluation of historical and geographic variation in semen quality. Kentaro Q Sakamoto, Mayumi Ishizuka, Akio Kazusaka, Shoichi Fujita. Jpn. J. Vet. Res. 52( 2) : 85-94,2004. (http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/10513/1/52(2)_85-94.pdf)
9. Clinical and Biological Consequences of Iodine Deficiency during Pregnancy. Glinoer D., Van Vliet G, Polak M (eds): Thyroid Gland Development and Function. Endocr Dev. Basel, Karger, 2007, vol 10, pp 62–85. (http://www.iccidd.org/cm_data/2007_Glinoer_Consequences_of_ID_during_Pregnancy.pdf)
10. Estrogenic chemicals often leach from BPA-free plastic products that are replacements fro BPA-containing polycarbonate products. Bittner G, Yang C, et al. Environmental Health 2014, 13:41.
11. The Effect Iodine Supplement on the Sexual Activity And Semen Characteristics of Friesian Bulls. Barakat T.M. Benha Vet. Med. J., Vol 15, No 2, Dec 2004. (http://www.fvtm.bu.edu.eg/fvtm/images/Animal_dept/pdf-Magazines/2-barakat2.pdf)
There are so many mixed messages about iodine supplementation and hypothyroidism. Some say you need to reduce iodine to help with symptoms, and some like Dr. Abraham and Dr. Brownstein say you need to supplement.
Increased iodine, especially in supplement form, can cause an increase of autoimmune attacks on the thyroid, but if selenium is supplemented at the same time, this doesn’t happen… I think. Haha, I wish I understood it all better, and I wish the messages weren’t so mixed!
Good on you Terri for teaching yourself all about iodine, and trying to teach us :).