Thyroid Disorders & Female Fertility

Thyroid Disorders & Female Fertility

Thyroid Disorders: What is the thyroid?

The thyroid is a butterfly-shaped gland located at the front of the neck, and it plays an extremely important role in many of the body’s functions. When a problem occurs, the thyroid may develop nodules and may either underfunction or overfunction, leading to the production of an incorrect amount of hormones. When thyroid dysfunction is present, symptoms typically appear because as the level of thyroid hormones in the body increases, the TSH (thyroid-stimulating hormone) level decreases to progressively lower values.

What are T3 and T4 hormones?

The thyroid gland produces the hormones thyroxine or tetraiodothyronine (T4), triiodothyronine (T3) and calcitonin. The hormones T3 and T4 contain iodine and regulate the way our body uses energy. T3 and T4 increase what is called <basal metabolism>, meaning they increase the amount of energy our body uses. T3 and T4 are secreted by the thyroid gland when it receives the hormonal signal from the hormone TSH. This hormone is secreted by an area of the brain called the pituitary gland. TSH secretion is stimulated by the secretion of the hormone TRH from another area of the brain called the hypothalamus. TRH is secreted when T3 and T4 levels are low. The hormone calcitonin is necessary for regulating calcium levels in the blood.

Thyroid conditions that most commonly affect women:

• Hyperthyroidism
– Hypothyroidism
– Thyroiditis (especially postpartum thyroiditis)
– Goiter
– Thyroid nodules
– Thyroid cancer

Hyperthyroidism: Excessive production of thyroid hormones

Hyperthyroidism is an overactivity or excessive production of thyroid hormones (FT3 and FT4) in the body. The symptoms are exactly the opposite: tachycardia, diarrhea, nervousness, weight loss, hypertension, loss of bone mass, sweating, feeling hot, eye disorders (redness, dryness, tearing or irritation of the eyes, photophobia, or even upper eyelid retraction that creates a “bulging” or aggressive look, etc.). There is also the possibility, in the case of subclinical hyperthyroidism and subclinical hypothyroidism, that there are no clear but rather atypical symptoms.

In hyperthyroidism, the patient should be protected nutritionally against weight loss by eating larger amounts of food each day, in order to get the energy needed to keep their weight stable. It is important to cover the increased calcium needs by eating more dairy products during the day (2-3 servings daily) and by taking calcium supplements, if the doctor considers it necessary. In case of diarrhea, intake of insoluble fiber (bran, peels, raw vegetables) should be limited, while soluble fiber (oats, banana, peeled apple) and probiotics help, either through foods (e.g. yogurt, yogurt drinks) or through supplements. Attention should also be paid to replacing fluids and electrolytes (sodium, potassium, chloride), because losses due to diarrhea are large.

When the gland underfunctions, it is called hypothyroidism. Hypothyroidism occurs when the thyroid gland fails to produce a sufficient amount of thyroid hormone for the body’s needs. Symptoms include fatigue, tiredness, sleepiness, constipation, excess weight (because the body’s energy expenditure decreases), increased feeling of cold, hoarseness, dry skin, thin and brittle hair, hair loss, menstrual disorders, anemia, sadness or even depression, dental problems, etc.

In hypothyroidism, the nutrition-related factors that need attention are the B-complex vitamins, vitamins A, C and E, and zinc, which play a role in hypothyroidism. If constipation occurs, fiber intake (whole grain products, vegetables, legumes) should be increased to an adequate level, fluid intake should also be adequate, and probiotics should be included in the daily diet. Cruciferous vegetables (Brussels sprouts, broccoli) and soy contain substances that affect thyroid function only in very large amounts and mainly when there is iodine deficiency. In normal amounts, and especially when cooked, they do not need to be avoided.

Thyroid and Blood Tests

Blood tests used to check the levels of your thyroid hormones (T3, T4, TSH, etc.), as well as thyroid antibodies, can confirm whether your thyroid is overactive, underactive, or functioning normally.

If there are relevant indications from the blood tests or from the clinical examination (if the endocrinologist has palpated a nodule), you may need to undergo an ultrasound, which will show the morphology of the thyroid (size, texture, presence or absence of nodules, etc.).

If nodules are present (especially if they are large), the doctor may recommend a scintigraphy scan, which provides information about their functionality — whether a nodule is “hot” or “cold” (cold nodules are more suspicious for malignancy than hot ones), whether it is toxic, etc.

If the nodules are suspicious, the next step will be a fine-needle aspiration (preferably under ultrasound guidance), where a special needle is used to collect cells from the nodules to investigate the possibility of malignancy.

A thyroid ultrasound also helps in diagnosing Hashimoto’s disease, because it can very early show initial changes in the size and structure of the thyroid gland — such as enlargement, heterogeneity, hypoechogenicity, nodules, and increased vascularity of the gland.

People with Hashimoto’s thyroiditis may have no symptoms for several years, but many will develop hypothyroidism over time, which is why regular TSH testing is needed.

Postpartum Thyroiditis

Postpartum thyroiditis is inflammation of the gland that occurs in about 5 to 10% of women after giving birth. It is often not diagnosed in time. Women with postpartum thyroiditis may feel very tired and low in mood. The disease often occurs in two phases: in the first phase (1-4 months after birth), symptoms of hyperthyroidism appear. This phase lasts about 1-2 months. In the second phase (4-8 months after birth), symptoms of hypothyroidism appear. This phase can last 6-12 months.

Women at higher risk of developing postpartum thyroiditis include those with:

• Autoimmune disease
• Type 1 diabetes mellitus
• Family history of thyroid disorders
• Postpartum thyroiditis in a previous pregnancy
• Chronic viral hepatitis

Female Hormones and Thyroid Hormones: Infertility

Just like the thyroid gland, the ovaries are stimulated by the brain and controlled by the hypothalamus and the pituitary gland. When long-term imbalances occur in the hypothalamus–pituitary–thyroid axis, problems in metabolism (due to the thyroid) and reduced ovarian function may develop. In extremely rare cases, since the body is already affected by one autoimmune disorder, it may also develop an autoimmune condition of the ovaries, where the body mistakenly produces antibodies against the ovarian tissue.

In premature ovarian insufficiency, treatment with estrogen and progesterone replaces the missing hormones and protects the bones and heart, but it does not restore fertility.

A lack of thyroid hormones can affect the ability to conceive in several ways. Hypothyroidism causes an increase in prolactin, disrupts the secretion of gonadotropins from the pituitary gland, affects adequate progesterone production, and influences estrogen metabolism, among other mechanisms. Therefore, it reduces fertility by causing irregular menstrual cycles, reduced frequency of ovulation, and impaired embryo implantation. Treatment with levothyroxine restores normal hormonal balance, regulates the menstrual cycle, and increases the chances of natural conception.

Mild hyperthyroidism does not seem to affect fertility to the same extent as hypothyroidism. Most women with mild thyroid overactivity may notice changes in the duration and amount of menstrual bleeding, but ovulation is usually not impaired. Women with low TSH but normal thyroid hormone levels do not require treatment, only close monitoring. This is not the case in severe hyperthyroidism (when thyroid hormones are significantly above normal levels). In these cases, menstruation may cease.

In general, autoimmune thyroid diseases are particularly common in young women. The presence of autoantibodies at very high levels (even when the thyroid is functioning normally) is associated with twice the likelihood of infertility.

Thyroid Disorders and Pregnancy

Pregnancy, even in women without any thyroid problem, causes significant changes in thyroid hormone levels. This can affect the course of the pregnancy and the developing fetus, as well as the mother’s health during pregnancy and after childbirth. Diagnosing and treating thyroid disease during pregnancy requires specialized management.

Thyroid Disorders in Pregnancy: Risks

1. Increased risk of miscarriage
2. Preeclampsia
3. Impaired brain development of the baby
4. Preterm birth and low birth weight
5. Fetal and neonatal tachycardia

Hypothyroidism should be corrected before or in the early stages of pregnancy. The first trimester is very important for the fetus, because this is when organogenesis takes place, that is, the formation of the various organs and above all the brain. The fetal thyroid starts producing hormones at around 12 weeks and only functions adequately later, which is why in the first half of pregnancy the fetus depends on the mother’s hormones. If hypothyroidism is not treated in time, it is a dangerous condition, because there is an increased risk of neurological defects in the fetus and impaired intellectual development after birth.

Hyperthyroidism during pregnancy may cause several complications for both the mother and the fetus. Miscarriage, excessive increase in blood pressure, preterm labor, fetal growth restriction, fetal tachycardia, and low birth weight are only some of these problems.

The good news, however, is that most thyroid problems are manageable when diagnosed early, and with proper monitoring, everything can be effectively treated.

Thyroid testing before pregnancy and IVF

Not every woman needs extensive thyroid testing. However, a TSH measurement, often together with anti-TPO antibodies, is recommended before conception when there is:

• A history or symptoms of thyroid disease, goiter or previous thyroid surgery.
• Type 1 diabetes or another autoimmune disease.
• A family history of thyroid disease.
• Infertility, irregular cycles or recurrent miscarriage.
• Age over 30 or severe obesity.

TSH is almost always checked before in vitro fertilization starts. Ovarian stimulation raises estrogen levels considerably, increases the need for thyroid hormones and can “unmask” borderline hypothyroidism. Women who already take thyroxine often need retesting during treatment.

Thyroxine in pregnancy: practical rules for taking it

• Take the pill on an empty stomach, with water, 30 to 60 minutes before breakfast and coffee.
• Keep at least four hours between it and prenatal vitamins, iron and calcium, which reduce absorption.
• As soon as you get a positive test, let your doctor know. The dose is often increased right away, for example with two extra doses a week.
• TSH is checked about every four weeks until mid-pregnancy and at least once at around 30 weeks.
• After childbirth, the dose usually returns to the pre-pregnancy dose, with a check at about six weeks.

Thyroxine is the same hormone the body produces. It is safe during pregnancy and breastfeeding, while stopping it without medical advice is much more dangerous than continuing it.

Iodine and the thyroid in women of reproductive age

Iodine is the raw material for thyroid hormones. The requirement is about 150 micrograms a day and rises to about 250 during pregnancy and breastfeeding, because the fetal brain depends on it. Good sources are iodized salt, fish, seafood, dairy products and eggs.

Many pregnancy supplements already contain iodine. Too much, however, is harmful: seaweed (kelp) products or very high doses can disrupt the thyroid, especially in women with Hashimoto’s. Selenium is often suggested for elevated antibodies, but the data are not enough to recommend it for all women trying to conceive.

Hyperthyroidism in pregnancy: what changes in treatment

In the first trimester, the pregnancy hormone hCG stimulates the thyroid and can temporarily lower TSH, especially when there is severe nausea and vomiting. This temporary condition usually does not need antithyroid medication and resolves by 18 to 20 weeks.

Graves’ disease is a different matter. In the first trimester propylthiouracil is usually preferred, and later a switch to methimazole may be made, at the lowest dose that controls the disease. TRAb antibodies are measured during pregnancy because they cross the placenta and can affect the fetal thyroid. Radioactive iodine treatment is contraindicated in pregnancy, and after it you need to wait at least six months before trying to conceive.

Frequently Asked Questions