Is Pregnancy Safe with Hypothyroidism?

By (gynecologist), (embryologist), (gynecologist) and (invitra staff).
Last Update: 12/01/2020

Hypothyroidism is a disorder characterized by a low production of thyroid hormones by the thyroid gland. This pathology is relatively common and can be treated successfully.

In some cases, the symptoms of hypothyroidism are subtle and may be confused with other conditions. Therefore, a person can go undiagnosed for several years. In contrast, other hypothyroid people report weight gain and decreased libido.

The most common cause of hypothyroidism is an autoimmune problem. Some immune system antibodies attack the thyroid gland and alter the manufacture of its hormones, which can lead to problems in pregnancy. However, this is not the only reason a woman may have difficulty achieving a pregnancy.

What is hypothyroidism?

Hypothyroidism is a condition characterized by an under activity of the thyroid gland, i.e. a reduced activity of the gland. This leads to an insufficient production of thyroid hormones and a decrease in the body's vital functions.

Hypothyroidism is a condition present in both men and women, although it is more common in the female population.

The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are responsible for stimulating the tissues to make proteins, as well as increasing the amount of oxygen in the cells.

These hormones are secreted by the epithelial cells of the thyroid gland through the use of iodine contained in food. The secretion of the hormones T3 and T4 is regulated by the thyroid-stimulating hormone (TSH), which is produced by the pituitary gland.

Thus, if the levels of thyroid hormones are low, the pituitary gland stimulates increased production of TSH hormone to promote the thyroid gland to produce more hormones. If T3 and T4 levels are too high, the pituitary gland produces less TSH.

Types of hypothyroidism

Primarily, hypothyroidism can be classified into two types depending on the trigger:

Primary hypothyroidism
is the most common form of the disease. In this case, the condition is caused by a failure of the thyroid gland itself. In addition, TSH hormone levels are elevated.
Secondary hypothyroidism
caused by an alteration in the pituitary gland, leading to a decrease in TSH values.

Apart from these two types of hypothyroidism, it is also important to consider peripheral or tertiary hypothyroidism. This condition is rare and is usually caused by the inability of tissues to respond to thyroid hormones or by peripheral inactivation of thyroid hormones. In this case, the alteration is at the level of the hypothalamus.

Causes and risk factors

Hypothyroidism can affect anyone, regardless of age or gender. Among the most common possible causes of thyroid gland disorders is the destruction of the gland by Hashimoto's thyroiditis, an autoimmune disease that is quite common in the female population. This pathology is characterized by the attack of cytotoxic T-lymphocytes on the thyroid gland.

Approximately 4 out of every 1,000 women develop this autoimmune condition. In contrast, the prevalence of Hashimoto's thyroiditis in the male population is 1 per 1,000 males.

In addition, there are different factors that can increase the risk of hypothyroidism. Some of them are described below:

  • Radioactive pre-treatment of iodine to the neck or chest.
  • Thyroid surgery.
  • Autoimmune diseases such as rheumatoid arthritis, lupus and diabetes.
  • Genetic disorders such as Turner's Syndrome and Down's Syndrome.
  • Administration of certain drugs, such as amiodarone and interferon.
  • After giving birth.

It should be noted that these are risk factors and do not mean that everyone in one of these situations will develop hypothyroidism.


The symptoms of hypothyroidism depend on each person and are difficult to perceive, sometimes even confused with symptoms of depression. Among the most common clinical manifestations of hypothyroidism are the following:

  • Constipation or hard stools.
  • Pale or dry skin.
  • Swelling of the face, hands and feet.
  • Increased body weight.
  • Abundant and abnormal menstrual periods.
  • Decreased libido.
  • Muscle and joint pain.

These are the most common symptoms of hypothyroidism, but it does not mean that a person diagnosed with this condition will have all the clinical manifestations. In addition, high blood cholesterol concentrations are quite common in hypothyroid people.

Diagnosis of hypothyroidism

Hypothyroidism can be diagnosed through the patient's clinical signs and laboratory tests. The specialist will order a blood test to study the values of thyroid hormones and thyroid-stimulating hormones (TSH).

The reference values for these hormones in adults are as follows:

  • TSH of 0.4 to 4.5 muI/L.
  • T3 of 3.5 to 7.8 muI/L.
  • T4 from 9 to 25 pmol/L.

It should be noted that these values may vary slightly depending on the laboratory in which it is performed.

In addition, determining TSH levels in the blood can help diagnose subclinical hypothyroidism, a type of condition that does not cause signs and symptoms in people. In these people's blood tests, T3 and T4 levels are normal, but TSH is above baseline.

In those cases where a goiter is present in the patient, the doctor will also request a thyroid ultrasound.


Treating hypothyroidism is very simple. The most common way to treat this pathology is the daily administration of a thyroxine pill since it has a long half-life and part of it is transformed into T3 in the body.

The doctor will take special care of people with heart problems and elderly patients, so treatment will start with low doses of medicine. In addition, in situations of stress, the specialist will advise increasing the doses of thyroid hormones, just like in pregnancy.

Hypothyroidism and infertility

Hypothyroidism can affect fertility by reducing egg production, and it also causes irregularities in the menstrual cycle. In addition, a deficit of thyroid hormones leads to increased levels of prolactin, a hormone that prevents ovulation in non-pregnant women when in high concentrations.

The reproductive system, both male and female, needs a sufficient amount of thyroid hormones to function properly. If pregnancy is achieved, hypothyroid women should be especially careful, as low levels of thyroid hormones are associated with an increased rate of miscarriage.

Considering undergoing a fertility treatment? By getting your individual Fertility Report your will see different clinics especially selected for you out of the pool of clinics that meet our strict quality criteria. Moreover, it will offer you a comparison between the fees and conditions each clinic offers in order for you to make a well informed choice.

In summary, hypothyroid women have high rates of infertility, failure of in vitro fertilization (IVF) cycles, and an increased risk of pregnancy complications if not treated properly.

Problems in pregnancy

As mentioned above, hypothyroidism can occur during or after pregnancy. Unfortunately, many of the symptoms of hypothyroidism can be confused with those of pregnancy and, as a result, the disease is neither treated nor diagnosed.

In pregnant women, hypothyroidism can cause miscarriage which is four times more likely than normal. That's why it's important to find out about possible hypothyroidism before pregnancy or very early on.

If there is no diagnosis and treatment for hypothyroidism, pregnant women are at risk of developing high blood pressure, having a premature delivery, and the babies may not reach full intellectual development.

Instead, those patients diagnosed with hypothyroidism will take medication based on hormone replacement therapy in an orderly and correct manner. The dose would probably have to be increased a little since pregnancy is a strain on the thyroid.


When a hypothyroid woman becomes pregnant, either naturally or through assisted reproduction, she will need to see a doctor as soon as she learns that she is pregnant. Depending on the results of the analyses performed, the specialist will adjust the dose of medication for a safe pregnancy.

On the other hand, thyroid medication should be taken on an empty stomach, at least one to two hours before or after meals. These drugs should not be given along with antacids and/or vitamins.

Finally, an iodine-rich diet is essential for hypothyroid people. Some recommended foods are iodized salt, white fish, bluefish, and seafood, among others. Also, try to avoid eating raw cabbage, red cabbage, and radish salads, as well as soybeans.

FAQs from users

Is hypothyroidism linked to infertility in women?

By Rut Gómez de Segura M.D. (gynecologist).

Yes, any alteration of the hormonal function affects the rest of the hormones and, therefore, can influence the reproductive function of both women and men.

In the case of women, alterations in ovulation have been reported and a higher rate of miscarriages in patients who present altered values in their thyroid hormones.

Sometimes, hypothyroidism is caused by immunity, and hyperimmunity itself can be associated with a decline in fertility.

How is infertility treated in women with hypothyroidism?

By Laura García de Miguel M.D., M.Sc. (gynecologist).

Women who have hypothyroidism suffer from a slowdown in the production of hormones by the thyroid gland.

In these women, it is necessary, regardless of the technique used (fertilization in vitro, ovodonation), to correct with thyroid hormone (oral tablets) until a good TSH is obtained, below 2.5 (thyroid hormone) to guarantee that the implantation can be produced without problems.

This treatment will continue until pregnancy and it is important to make periodic controls with the endocrinologist to evaluate if it is necessary to increase or decrease the doses of the treatment.

Is hypothyroidism hereditary?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

There are numerous studies that indicate the existence of genetic predisposition, but they do not claim that hypothyroidism is inherited as such. This means that there is a greater possibility of suffering from hypothyroidism if a family member has the disease.

On the other hand, it is essential to take into account the type of hypothyroidism. In the case of hypothyroidism due to autoimmune causes, genetics plays a more relevant role.

What is Hashimoto's disease?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

Hashimoto's disease, also called Hashimoto's thyroiditis, is an autoimmune disease characterized by the production of antitheroidal antibodies
that attack the thyroid gland itself.

This disease is the most common cause of hypothyroidism. Its prevalence is 4 out of every 1,000 women of average age, although it can also manifest itself in men and children.

Sometimes, Hashimoto's thyroiditis can be accompanied by other pathologies such as diabetes, pernicious anemia and rheumatoid arthritis, among others.

Suggested for you

Besides hypothyroidism, there are other pathologies that cause infertility in women due to alterations in the thyroid gland. If you want to read information about all of them, we recommend you visit the following article: Female infertility due to thyroid gland problems.

On the other hand, the woman's fertility tests include a blood test where the values of thyroid hormones are evaluated, but also other hormone levels. Here is the link in case you want to know more: Female hormone tests: what are the normal levels?

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FAQs from users: 'Is hypothyroidism linked to infertility in women?', 'How is infertility treated in women with hypothyroidism?', 'Is hypothyroidism hereditary?' and 'What is Hashimoto's disease?'.

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Authors and contributors

 Laura García de Miguel
Laura García de Miguel
M.D., M.Sc.
Bachelor of Medicine and Surgery from the Autonomous University of Barcelona, with specialization in Obstetrics & Gynecology at Sant Joan de Déu University Hospital. Master's Degree in Human Reproduction from the Complutense University of Madrid. Currently, she is the Medical Director of Clínica Tambre in Madrid, Spain. More information about Laura García de Miguel
License: 280843059
 Marta Barranquero Gómez
Marta Barranquero Gómez
B.Sc., M.Sc.
Graduated in Biochemistry and Biomedical Sciences by the University of Valencia (UV) and specialized in Assisted Reproduction by the University of Alcalá de Henares (UAH) in collaboration with Ginefiv and in Clinical Genetics by the University of Alcalá de Henares (UAH). More information about Marta Barranquero Gómez
License: 3316-CV
 Rut Gómez de Segura
Rut Gómez de Segura
Graduation in Medicine and Surgery from the University of Alcalá de Henares. Specialization in Obstetrics and Gynecology at the Hospital Costa del Sol in Marbella. Dr Rut Gómez de Segura currently works as medical director in the fertility center ProcreaTec in Madrid. More information about Rut Gómez de Segura
Licence number: 28/2908776
Adapted into english by:
 Romina Packan
Romina Packan
inviTRA Staff
Editor and translator for the English and German edition of inviTRA. More information about Romina Packan

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