Infertility, Miscarriage, and Subclinical Hypothyroidism

Infertility, Miscarriage, and Subclinical Hypothyroidism

I wish more than anything I had found a good thyroid doctor before I miscarried my baby unnecessarily to hypothyroidism. My child may be alive today.

I hope this article by New York City reproductive endocrinologist Dr. Hugh Melnick finds all the women struggling with infertility and miscarriage.

Written by Hugh D. Melnick, MD, FACOG

As a doctor helping women conceive and carry pregnancies to the point of having a healthy baby for over 35 years, I have noticed that recognizing and treating thyroid problems was essential in helping both conception and reducing miscarriage. I remember the early days in my career, when blood testing was just being developed and doctors relied on listening to a patient’s symptoms in order to make a diagnosis. In those days, if a woman had some or all of the typical symptoms of hypothyroidism, she was given a prescription for a natural thyroid medication and observed for the improvement in her symptoms and for conception to occur. Almost all women who had miscarriages were treated with thyroid medication and many eventually completed successful pregnancies. The practice of medicine in those days was much less complex and doctors treated patients symptomatically. In many cases, such treatments can be very successful. After all, “if it looks like a duck, walks like a duck and it quacks, it is a duck!”

Unfortunately in many cases today, when doctors rely only on a few blood tests to diagnose hypothyroidism, an obvious diagnosis will often be missed. There are several scientifically valid, complex technical reasons that explain why thyroid blood tests can actually be misleading in many cases. The most important one is that a person can actually be hypothyroid with the common thyroid blood tests being normal. Nearly forty years later, treating infertile couples with the cutting edge of the In Vitro Fertilization technology, I have had a “front row” view of the vast complexities involved in the process of conception. The genetic basis for 60% of cases of miscarriage has been scientifically demonstrated, so most miscarriages are the result of chromosomal problems that occur at the moment of actual conception. However, that leaves almost 40% of miscarriages as potentially being medically preventable.

Since hypothyroidism is quite common in the female population (up to 30% are treated for hypothyroidism in some surveys), I believe that natural thyroid treatment could potentially save a significant number of genetically normal pregnancies, in cases in which a woman has clinical symptoms of hypothyroidism. In my own clinical experience, both the rate of conception is improved and incidence of miscarriage is reduced when women with the typical symptoms of an under active thyroid gland, but have “normal” blood test results, are treated adequately with natural thyroid hormone supplementation. By adequate treatment, I mean that a woman is treated with gradually increasing doses of natural thyroid medication, until her symptoms improve. Although I do monitor blood tests, the levels in blood indicate that the medicine is being absorbed and gets into the circulation. It does not indicate the adequacy of the dose or whether too much medication is being taken (when a patient is on natural thyroid medication, many doctors will misinterpret blood test results and mistakenly think that the patient is hyper(overactive)thyroid.

There are frequent cases of “unexplained infertility” in which all factors that could cause infertility are found to be normal, yet pregnancy does not occur naturally or with fertility treatments. Unfortunately, many such cases are attributed to stress or to psychological factors. When questioned closely, many of these women do have symptoms that are typical of hypothyroidism. I find that in this group thyroid supplement treatment will often result in successful conception, either naturally or when combined with fertility enhancing therapy. The key to the successful diagnosis and treatment is that the physician asks the right questions to the patient in order to elicit whether the symptoms of hypothyroidism are present. It is also important that a patient feels free to discuss all her symptoms, related to fertility or not, with a physician. Thyroid treatment, once the proper dose is reached, takes 2-12 weeks to exert its effect on the cells of the body.

Certain thyroid blood tests, not routinely performed, are mandatory on all couples (both partners) having infertility issues and on any woman who has had miscarriages. These tests are called anti-thyroid antibodies (Anti-TPO and Anti-TG). When positive, these tests indicate that a person has an autoimmune condition known as Hashimoto’s thyroiditis. These tests may be positive in totally asymptomatic individuals, yet should be treated with thyroid medication if there is an infertility or miscarriage issue. All men should have thyroid tests done of there seems to be a problem with their sperm. I have seen cases in which pregnancy has occurred naturally after men were diagnosed and treated for Hashimoto’s thyroiditis. The thyroid gland is known as the master gland of the body, because thyroid hormones control the cell’s metabolism and ensures its proper biological function.

Below you will find a list of symptoms, both physical and psychological, that are experienced by women who have under-active thyroid function. These symptoms may vary in degree and in intensity.

Physical Symptoms of Under-Active Thyroid

Weight gain/ difficulty in losing weight
Always feeling cold, severely affected by cold weather, hands and feet always cold
Water retention
Dry hair and/or hair loss
Dry skin and brittle fingernails
Irregular periods, heavy menstrual flow, infertility, miscarriages
Joint or muscle pains
Carpal and/or Metatarsal Tunnel syndrome
Tingling or numbness of the hands or feet
Hearing Ringing or Ticking in the inner ear
Diagnosed with Chronic Fatigue Syndrome or Fibromyalgia

Psychological Symptoms of Under-Active Thyroid

Decreased Sex Drive
Mentally Foggy
Decreased Concentration
Poor Recent Memory
Postpartum Depression

Although it is not currently known exactly how hypothyroidism contributes to infertility and miscarriage, it is well known that the detrimental effect of inadequate amounts of thyroid hormone in the cells of body can be corrected by adequate thyroid hormone treatment, which results in successful conception and delivery of a healthy baby for many couples.

Thyroid-Screening in Pregnancy

I wrote an article regarding thyroid-screening in pregnancy published on January 7, 2015 in response to a viewpoint article that originally appeared in the October issue of the American Journal of Obstetrics & Gynecology. In my opinion, the authors erroneously concluded that routine thyroid screening in early pregnancy is not warranted. Of course, I think that this article is totally off base and I have discussed my objections to it. If left unchallenged, and if their conclusions are accepted as ‘gospel’ truth by the medical community, many pregnant women, who have undiagnosed hypothyroidism, will not be offered thyroid screening tests. The result would be that many undiagnosed women will not receive thyroid treatment that is needed to prevent the maternal and fetal complications associated with hypothyroidism.

To the Editors:
I would like to put the “to screen or not to screen” controversy into perspective. In my opinion, there really should be no debate about the issue of mandatory early prenatal testing for hypothyroidism. The authors correctly point out that hypothyroidism is the second most common condition that affects women of reproductive age. The frequency of the diagnosis reported in different studies will depend on the thyroid-stimulating hormone cutoff (2.5, 3.0, or >4.0 μ/L) and whether antithyroid antibodies were tested. Depending on the parameters used, the incidence of hypothyroidism reported in pregnancy varies greatly and can be estimated to be 4.0-15.5%.2, 3 Because in many studies thyroid screening tests were minimal and consist of TSH and free T4 only, the frequency of hypothyroidism in pregnancy may be underestimated.

The pregnant woman with hypothyroidism has been demonstrated to be at increased risk for miscarriage and other major gestational morbidities. Studies on the association of hypothyroidism with an increased risk of having a baby with some degree of intellectual or developmental impairment are conflicting and differ methodologically.

On the other hand, the cost of screening for hypothyroidism is extremely small on a per-patient basis; in the United States, a significant percentage of screening costs would be covered by health insurance plans.

According to compiled data from our practice (average reimbursements for thyroid tests performed in-house in our laboratory), the cost of minimal thyroid screening (which we believe to be inadequate) is $24.21 per patient. The per-patient cost of a comprehensive thyroid evaluation that consists of measurements of thyroid-stimulating hormone, total and free T4 and T3, and antithyroid peroxidase and antithyroglobulin antibodies is $87.20. Comprehensive thyroid screening is obviously preferable in that it is able to indicate several different etiologic types of hypothyroidism, Hashimoto’s thyroiditis in particular.

Comprehensive testing is inexpensive and casts a wide net in the identification of hypothyroid women early in pregnancy, when treatment is the most critical. With a small investment of <$100/per woman, the incidence of certain recognized gestational morbidities could be reduced. The question of the incidence of intellectual impairment and the effect of treatment on the offspring of women with an untreated hypothyroid is not answered completely, because there are confounding variables that could influence outcome.

Irrespective of cost, if it is possible to reduce intellectual compromise in any child by treating maternal hypothyroidism, it is worth doing so. The potential gain of early diagnosis and intervention in avoiding untoward fetal and maternal events that are associated with maternal hypothyroidism clearly outweighs the financial and emotional costs of poor outcomes that result from undiagnosed and untreated gestational hypothyroidism. Because there is really no “down side” to comprehensive thyroid screening, either before conception or in the early first trimester, there is no reason that it should not be recommended.

About Dr. Hugh D. Melnick

Hugh D. Melnick, M.D., F.A.C.O.G. is a reproductive endocrinologist who has been treating patients with hormonal and fertility problems since 1976. In 1983, Dr. Melnick founded Advanced Fertility Services, which was the first free standing In Vitro Fertilization Center in New York City and is still its medical director. He has been impressed by the large number of infertile women that he has seen over the years, who are symptomatically hypothyroid, and who conceive after treatment with thyroid medication.

READ NEXT: I lost my unborn baby needlessly. What I want other women to know about thyroid disease

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About Dana Trentini

Dana Trentini founded Hypothyroid Mom October 2012 in memory of the unborn baby she lost to hypothyroidism. This is for informational purposes only and should not be considered a substitute for consulting your physician regarding medical advice pertaining to your health. Hypothyroid Mom includes affiliate links including the Amazon Services LLC Associates Program.


  1. I learnt a lot about miscarriages that you have mentioned on this blog post. It really helpful who doesn’t aware about active thyroid, which is causes to miscarriage.

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