As someone approaching her mid-30s and hoping to start a family soon, I certainly don’t want to think about the quantity and quality of my eggs—both of which are essential for reproductive success—diminishing as I get older [1]. But for those of us currently on the path to parenthood, or who would like to have children in the future, understanding diminished ovarian reserve (DOR) can be important.
You may have heard of recommended treatments for low AMH/diminished ovarian reserve, some of which have more merit than others. Now a new study focuses on iodine’s potential capacity to make an impact on fertility outcomes—specifically by improving egg quality.
Diminished Ovarian Reserve (DOR): What it is, and why it happens
A woman is born with all the eggs she will ever have, and the number naturally diminishes as she ages. A woman is said to have ‘diminished ovarian reserve,’ when her ovaries have fewer eggs than expected for her age. The quality of the eggs may also be low.
While age is the most common cause of diminished ovarian reserve, there can be other factores at work: a family history of premature menopause; chemotherapy and radiation treatments; autoimmune and thyroid disorders; pelvic inflammatory disease caused by infections; environmental toxins; endometriosis of the ovaries; and even lifestyle factors like smoking, stress, lack of exercise, and poor nutrition.
Treatments for diminished ovarian reserve
For those diagnosed with DOR, recommended treatments first include improving one’s diet, reducing stress, and exercising regularly. Some women with DOR may be encouraged to use: fecundación in vitro (IVF), either with their own eggs or with donor eggs; intrauterine insemination (IUI) [2]; terapia hormonal sustitutiva to aid the menstrual cycle and lessen menopausal symptoms; and intervenciones quirúrgicas on the ovaries to help regulate ovulation.
A note on the evidence for IVF
As noted in this Natural Womanhood artículo, however, a Estudio de 2017 found that there was not a statistically significant difference in probability of conception between women with low ovarian reserve, and women with normal AMH and inhibin B values [3]. And, in 2024, otro estudio reaffirmed that ovarian reserve does not influence natural conception [4]. This means low AMH/DOR alone may not be an evidence-based reason for using IVF to conceive, especially given its risks for moms and babies.
Vitamins and supplements
On the other hand, some interventions may support and/or improve egg quality, which may help lead to healthy conception. Some suplementos, like CoQ10, have been shown to improve the maturation rate of eggs, embryo quality, and clinical pregnancy rate [5]. Vitamina D has been shown to improve egg quantity by increasing AMH [6], the hormone that interacts with Follicle-Stimulating Hormone to control follicle growth. Melatonin can also contribute to the maturation of eggs, fertilization, and embryonic development.
Notably, a small October 2025 study conducted in Iran and published in the journal Naturaleza found that iodine, a mineral that’s essential for thyroid health, metabolism regulation, and cognitive development in fetuses and children, may also have positive effects on fertility for women with DOR.
Could iodine supplementation make a difference in egg quality?
Prior studies have linked iodine deficiency with infertility—specifically, delayed conception and a “46% decrease in fecundability” [1]. We know that iodine deficiency can have a negative impact on thyroid hormone production, and that proper thyroid function is essential for fertility [7]. But the 2025 Iranian study was the first preliminary study to be conducted on the impact of iodine supplementation on oocyte quantity and quality, egg cell death (apoptosis), and successful DNA replication, repair, and assembly of early follicles through the Proliferating Cell Nuclear Antigen (PCNA), in women with DOR.
How the study was conducted
The experiment included ten Iranian women diagnosed with DOR who were between the age of 25 and 42 and candidates for IVF or congelación de óvulos. To qualify, these women also had to have: no history of smoking or substance abuse; no history of multiple miscarriages; no underlying medical conditions such as thyroid issues or endometriosis; and they had to agree to go through with two consecutive ovarian stimulation cycles.
The first cycle was conducted without iodine supplementation and followed the standard IVF protocol for ovarian stimulation. Prior to the second cycle, the participants took 150 micrograms of iodine daily for two months, which is the amount of iodine recommended by Iran’s national guidelines for those trying to conceive.
Resultados del estudio
Positive effects on cumulus cells—the ‘guardians’ of the egg
After iodine supplementation, there was a notable percentage increase in the number of live cumulus cells, which rose from 26.4% to 67.9%. Cumulus cells can be thought of as the overall ‘guardian’ of the egg, because they directly surround the egg within the follicle, and make sure eggs develop properly and are able to be fertilized. Cumulus cells are vital for egg development and growth prior to ovulation, because they facilitate the conversion of glucose to its metabolites—molecules that are necessary for regulation and support of cellular function in eggs [5]. Cumulus cells also regulate the egg’s cell division (meiosis) process to prepare it for fertilization, and produce hyaluronic acid to expand and help the egg release from the follicle [5] [6].
After iodine supplementation, there was a notable percentage increase in the number of live cumulus cells, which rose from 26.4% to 67.9%. Cumulus cells can be thought of as the overall ‘guardian’ of the egg, because they directly surround the egg within the follicle, and make sure eggs develop properly and are able to be fertilized.
Furthermore, early death of cumulus cells was reduced from 19.3% to 13.7%, and late death declined from 44.7% to 9.0%. While apoptosis is a controlled process of programmed cell death that helps to eliminate non-viable cumulus cells, a higher percentage of live cells is optimal for egg viability [8]. According to the study: “A delicate balance between pro-apoptotic and anti-apoptotic factors within these cells is essential for successful ovulation and embryo development.” From the study results, it appears that iodine helps to reduce death in these cumulus cells and maintain the balance required to produce quality eggs, a high fertilization rate, and a high quantity of eggs [1].
Effects on PCNA level and egg maturity
The Iranian researchers also found that an increase in Proliferating Cell Nuclear Antigen (PCNA) expression following iodine supplementation correlated with the decrease in early and late cell death. The PCNA level after supplementation was approximately 3.4 times higher than before supplementation. This higher level of PCNA was an indicator that cumulus cells were proliferating properly, or, actively growing and dividing.
Lastly, regarding egg quality after iodine supplementation, while there was not a significant increase in the number of immature or partially mature eggs retrieved, there was a notable increase in the number of fully mature eggs (M2), or the ones needed for successful fertilization. The number of M2 eggs grew from 1.9% to 3.2% [1].
The Iranian researchers therefore concluded that: “two months of iodine supplementation significantly improved oocyte quality and positively affected various aspects of cell function… These results suggest that iodine supplementation may have a beneficial effect on ovarian health and fertility potential” [1]. Importantly, for women with DOR/low AMH, this increase in egg calidad may be even more significant for actual fertility than one’s quantity of eggs is.
“two months of iodine supplementation significantly improved oocyte quality and positively affected various aspects of cell function… These results suggest that iodine supplementation may have a beneficial effect on ovarian health and fertility potential”
While this study does not report clinical findings like pregnancy or live birth rates, and further studies that include larger sample sizes and a placebo group are needed for further validation, this study was a vital first step in evaluating iodine’s impact on overall egg health in women with DOR.
Incorporating dietary iodine to improve egg quality?
Iodine is available as an over-the-counter supplement, typically in the form of synthetic potassium iodide or sodium iodide, although iodine naturally-derived from seaweed and kelp is also available in various supplement forms. (Note, however, that you shouldn’t supplement with iodine—or anything!—blindly. While healthy levels of iodine promote good thyroid function, exceso yodo can actually interfere with proper thyroid functioning [9].)
In addition to supplements, there are also many food-based sources of iodine. These sources include seafoods, milk and other dairy products, and eggs, all of which may improve egg quality and other fertility parameters. For those who don’t eat animal products, iodine can be found in seaweed and iodized salt.
While further studies are needed to definitively confirm the findings of this Iranian study, this preliminary research provides hopeful evidence for women struggling with DOR that iodine supplementation may indeed create a better environment for healthy egg development and fertilization.
