The thyroid is a gland located at the front of the base of the neck: it produces certain hormones necessary for multiple processes that occur within the body, including reproduction. As a result, its malfunction in women can interfere with conception and gestation.
Hypothyroidism, i.e. the insufficient production of thyroid hormones, is the most common among thyroid diseases: the most frequent form, autoimmune ones, affects about 2 percent of the Italian population.
What is hypothyroidism
We speak of hypothyroidism when the production of thyroid hormones (thyroxine or T4 and triiodothyronine or T3) is not sufficient for the needs of the body.
The most common form of hypothyroidism is the primary one, that is, it depends on a malfunction of the thyroid. This malfunction can be congenital, present from birth, or more often acquired. The first, if not detected immediately and treated, can cause cretinism, or growth retardation in the newborn, combined with a very serious form of mental and neurological deficit. Fortunately, this rarely happens today, thanks to routine screening at birth.
When it is acquired, however, primary hypothyroidism can be iatrogenic, that is, the consequence, for example, of excessive doses of antithyroid drugs, administered with the intention of treating a form of hyperthyroidism, or derive from the surgical removal of part or all of the gland due to other problems. It can also be caused by untreated viral infections that attack the thyroid. More often, however, it is an autoimmune form: the gland is attacked and destroyed by the antibodies produced by the body itself. Currently there is no precise knowledge about the causes of this autoimmune reaction.
Very rare, however, is central hypothyroidism, in which the insufficient production of thyroid hormones derives from a problem not of the thyroid, but of the pituitary and / or hypothalamus, two glands located in the brain that, through the production of a hormone, called TSH (the pituitary gland produces it on stimulation of the hypothalamus), normally push the thyroid to perform its function.
Symptoms
The main symptoms resulting from hypothyroidism are: asthenia, weakness, slowing down of metabolism, reflexes and mental processes, but also increased fluid retention, with a feeling of swelling, especially in the face (myxedema), constipation, sleep disorders, irritability, sometimes even depression.
These manifestations, especially when hypothyroidism is not marked, may be comparable to those of many other problems. It should not be forgotten, however, that there is also a subclinical hypothyroidism, which does not give obvious signs.
How it turns out
To diagnose hypothyroidism, a simple blood sample is first used to undergo the dosage of thyroid hormones (in particular FT4), TSH and anti-thyroid antibodies (anti-thyroperoxidase, AbTPO, and anti-thyroglobulin, AbTg).
TSH in primary hypothyroidism is generally high because the body tries to stimulate the thyroid more, while in the middle forms it is low or normal.
FT4 levels, on the other hand, are always low in forms of hypothyroidism, with the exception of subclinical hypothyroidism, where it is generally normal, while TSH is high.
It is usually sufficient to evaluate the TSH and, only if it is altered, check the FT4 values. However, when performing the examination for the first time, it is useful to combine FT4 with TSH even if the latter is normal: if FT4 is still low, it can signal central hypothyroidism.
The search for anti-thyroid antibodies is used to confirm whether or not it is autoimmune hypothyroidism: their presence, without alterations of TSH and FT4, is a sign that the body has a tendency to attack the thyroid, causing autoimmune thyroiditis which, in turn, is one of the causes of hypothyroidism. In this case, monitoring over time will be needed to intervene immediately in case of hypothyroidism.
The reference values of TSH, FT4 and thyroid antibodies (anti-thyroperoxidase and anti-thyroglobulin) may vary depending on age, sex and also the equipment used for their analysis. In addition, it is always advisable to evaluate the results of the examinations with your doctor or specialist. In the following table you will therefore find purely indicative values.
| What is it | “Busted” values | |
|---|---|---|
| TSH | Hormone produced by the pituitary gland that controls the secretory activity of thyroid hormones | First trimester:
< 0.1 mIU/L > 2.5 mIU/L Second trimester: < 0.2 mIU/L > 3 mIU/L Third trimester: < 0.3 mIU/L > 3-3.5 mIU/L |
| FT4 | Free thyroxine, the secretion of which is regulated by the hormone TSH. Regulates metabolic processes | < 0.8 ng/dL
> 1.8 ng/dL |
| Anti-thyroperoxidase (AbTPO) | Immunoglobulins produced against thyroid peroxidase, a protein located in the cytoplasm of thyroid follicular cells | > 35 IU/ml |
| Anti-thyroglobulin (AbTg) | Immunoglobulins produced against thyroglobulin, a protein synthesized by thyroid cells | > 115 IU/ml |
Finally, in case of primary hypothyroidism, an ultrasound of the thyroid can also be used to deepen the diagnosis to evaluate its appearance and the presence or absence of nodules or alterations.
The role of the thyroid in reproduction
Thyroid function has direct and indirect effects on ovulation, so much so that the presence of untreated dysfunction can compromise fertility. In particular, in case of hypothyroidism, the thyroid is overstimulated by the pituitary and hypothalamus so that it can do its job.Excessive stimulation of the thyroid gland can cause an increase in prolactin levels in the body which, in turn, interferes with ovulation and the menstrual cycle, making it irregular, in some cases until it disappears (amenorrhea).
Even during the nine months the thyroid plays an important role because the hormones it produces (thyroxine, triiodothyronine) intervene in the processes of growth and development of the fetus. For this reason, during gestation the gland is called to work higher than usual and must, therefore, be in excellent shape.
Hypothyroidism in pregnancy: the risks if it is not treated
As anticipated, during the nine months the thyroid is called to overwork. However, if there is an untreated dysfunction, this gland fails to perform its duty at its best, consequently increasing the risk of miscarriage, fetal death, pregnancy complications such as hypertension or gestational diabetes, placental abruption, preterm birth, low birth weight.
Some studies have also shown a reduced IQ in children born to women with very serious untreated hypothyroidism.
How to behave before having a child
If a woman is planning to become a mother, even if she apparently does not have thyroid problems, it is good to undergo the dosage of thyroid hormones and anti-thyroid antibodies.
The first test is used to evaluate the functioning of the gland and discover the possible presence of a dysfunction. Many women, in fact, do not know that they suffer from hypothyroidism: if this is detected, it must be treated before embarking on pregnancy.
The dosage of antibodies, on the other hand, serves to discover the possible predisposition to develop these dysfunctions, which can occur for the first time during gestation due to the strain to which the gland is subjected in nine months.
The evaluation of thyroid function is also important in view of a possible use of assisted fertilization, because the hormonal treatments to which one undergoes in these cases inevitably affect the gland.
How to behave in pregnancy
Pregnant women with hypothyroidism should continue treatment for their dysfunction even during the nine months. The treatment of hypothyroidism is chronic and involves the daily intake, at physiological doses (ie superimposable to those that would be produced by the thyroid under normal conditions) of the hormone thyroxine, in the form of levothyroxine sodium.
The intake of levothyroxine does not represent a risk for the unborn child, but rather it is fundamental for its development because it complements the maternal hormone production that is insufficient. It will be up to the doctor to adapt the hormonal dosage to the woman’s new condition.
In the case of positive antibodies, however, the woman will have to undergo frequent thyroid control during pregnancy to discover any hypothyroidism in the bud and be able to intervene with appropriate treatment. It is necessary to undergo a dosage of thyroid hormones approximately every 3-4 weeks for the first three months of pregnancy (it is the phase in which the demands to the maternal thyroid are greater, because the baby’s organism is being formed) and continue once a trimester for the remaining six months of gestation. If tests reveal hypothyroidism during pregnancy, levothyroxine replacement therapy is indicated.
To meet the needs of the maternal body and the fetus, the thyroid also needs an adequate amount of iodine (which is an essential component of thyroid hormones) introduced through the diet, otherwise its deficiency can lead to the risk of developing thyroid insufficiency during pregnancy and that, later, a nodular goiter may develop (increase in thyroid volume, with nodule formation).
For this reason, all pregnant women, even those whose thyroid is in perfect health, should take iodine daily, for example by replacing traditional table salt with iodized salt. It may also be recommended during pregnancy and lactation to take, on medical advice, multivitamin supplements containing 150 micrograms of iodine.
What to do after childbirth
5% of new mothers experience thyroid dysfunction (called postpartum thyroiditis) in the 12 months following delivery, which can, if left untreated, lead to hypothyroidism. This happens in particular in those who have anti-thyroid antibodies that can activate immediately after delivery and attack their target.
If, in fact, during pregnancy the maternal immune system goes through a sort of tolerance phase so as not to attack the child (which half has the paternal genetic heritage and therefore is an external and potentially attackable entity), after birth the maternal defenses awaken. For this reason, even in the months following childbirth, women in whom anti-thyroid antibodies are present should undergo monitoring of gland function, according to the times recommended by the doctor (be it the gynecologist or the specialist in endocrinology).
Joycelyn Elders is the author and creator of EmpowerEssence, a health and wellness blog. Elders is a respected public health advocate and pediatrician dedicated to promoting general health and well-being.
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