Thyroid nodules in pregnancy | Symptoms, diagnosis, treatment methods!

Thyroid nodules in pregnancy

Pregnancy is accompanied by extensive hormonal and physiological changes. These changes can affect the function of the thyroid gland in various ways. One of the possible consequences of these changes is the occurrence or exacerbation of thyroid disorders, including thyroid nodules. A pregnant woman may have thyroid nodules before pregnancy or develop this problem during pregnancy. Therefore, regular monitoring of the thyroid status during this period is of particular importance to maintain the health of the mother and fetus.

Symptoms of thyroid nodules in pregnancy

The symptoms of thyroid nodules in pregnancy are the same as the symptoms of thyroid nodules in ordinary people. However, the physiological and hormonal changes of pregnancy may make it more difficult to interpret some of the symptoms and make an accurate diagnosis. The most important symptoms of thyroid nodules in pregnancy include the following:

A lump or bump in the neck: The main symptom of a thyroid nodule. The thyroid nodule may be felt to the touch or only detectable on ultrasound.

Voice change or hoarseness: Voice change is one of the possible symptoms of a thyroid nodule. Large nodules can cause hoarseness, hoarseness, or a change in pitch by pressing on the laryngeal nerve. During pregnancy, changes in voice may occur due to hormonal changes; but the presence of a nodule can exacerbate these changes. Therefore, any abnormal voice change during pregnancy should be checked by a doctor.

Neck pain: Neck pain during pregnancy has various causes, one of which is a thyroid nodule. Dull pain or pressure in the front of the neck can indicate a nodule growing or pressing on surrounding tissues.

Difficulty swallowing or breathing: Very large thyroid nodules can cause difficulty swallowing and breathing by pressing on the trachea and esophagus. Although these symptoms are rare, they may indicate significant growth of the nodule and require immediate investigation; especially if they are accompanied by other symptoms of a thyroid nodule.

Diagnosis of thyroid nodules during pregnancy

Pregnancy does not affect the methods of diagnosing thyroid nodules. In fact, the tests for diagnosing thyroid nodules during pregnancy are the same as at other times. However, the interpretation of the test results will be slightly different depending on the pregnancy conditions. The following are the most important methods used to diagnose thyroid nodules during pregnancy.

Physical examination

Neck examination is the first step in diagnosing thyroid nodules during pregnancy; but it cannot be a definitive diagnostic method alone. Physical examination of the neck is effective in diagnosing large and superficial nodules. During pregnancy, the thyroid gland may become slightly larger due to increased blood volume and hormonal changes. This makes it more difficult to diagnose smaller or deeper nodules with a physical examination. Also, a physical examination cannot determine whether the nodule is benign or malignant.

A physical examination of the neck can be performed at any time during pregnancy; it is especially recommended at the end of the first trimester. If there are suspicious symptoms or changes in the size of the thyroid gland, the physical examination may be repeated at subsequent visits. The neck examination is performed in a sitting or standing position. The doctor gently palpates the neck and thyroid gland with his fingers to check for any lumps, bumps, or changes in the size of the thyroid gland. The patient is usually asked to swallow during the examination.

Measuring TSH Levels

Measuring TSH is necessary during this period, and its results should be interpreted according to the trimester of pregnancy. In the first trimester of pregnancy, TSH levels decrease in some women due to the stimulating effect of the hormone hCG. This decrease is more pronounced in twin pregnancies. Low TSH levels in the first trimester can indicate transient thyrotoxicosis of pregnancy, which may be accompanied by severe nausea and vomiting. The diagnosis of a functional nodule is only made if TSH levels are undetectable in the first trimester and remain the same in the second trimester. Undetectable means that the level of TSH (thyroid stimulating hormone) in a blood test is so low that it cannot be measured by standard laboratory methods.

Toxic nodules are a rare cause of hyperthyroidism in pregnancy. If Graves’ disease is suspected with a non-functioning nodule, an anti-TSHR antibody test is essential for diagnosis. TSH measurement is very important for thyroid nodules diagnosed during pregnancy. If the TSH level is less than 0.1 mIU/l and remains the same in the second trimester, the nodule is considered functional during pregnancy.

Ultrasound

Nodules that are already present and those that appear during pregnancy may require different evaluation and management. Since ultrasound is safe during pregnancy, it is used as the main method for diagnosing thyroid nodules in pregnancy. The EU-TIRADS classification, which is derived from the ultrasound results, determines the probability of benign and malignant nodules. If the benignity of a thyroid nodule was confirmed by ultrasound or biopsy before pregnancy and less than 2 years have passed since this diagnosis, there is no need for further ultrasound or biopsy. This means that the pregnant woman can be assured that the thyroid nodule in question will not progress during pregnancy. However, careful palpation and examination of the neck is recommended at the end of the first trimester. In the event of symptoms such as neck discomfort (especially when swallowing) or an increase in the size of the nodule or the appearance of lymphadenopathy on palpation of the neck, ultrasound should be performed as soon as possible.

Fine needle aspiration biopsy (FNAB)

In this procedure, a sample of nodule cells is removed using a thin needle and examined in a laboratory. This procedure helps the doctor make a definitive diagnosis of whether the nodule is malignant or benign. The decision to perform a thyroid nodule biopsy during pregnancy should be made carefully and based on the specific circumstances of each individual by a specialist doctor. In general, doctors try to postpone thyroid nodule biopsy during pregnancy as much as possible. This is because of the potential risks to the fetus and mother. However, in some special cases, a biopsy is necessary; including:

• If an ultrasound shows that the nodule has very suspicious features (such as an irregular shape, unclear margins, or the presence of abnormal blood vessels), the doctor may recommend a biopsy.
• In particular, a biopsy is necessary if the nodule is classified as EU-TIRADS 5 (i.e., very likely to be malignant) and is larger than 1 cm in size, or if the lymph nodes in the neck appear suspicious.
• If the nodule is causing problems such as difficulty swallowing, voice changes, or neck pain, the doctor may recommend a biopsy to determine the cause of these symptoms.

The timing of the biopsy depends on the doctor’s opinion and is determined by the patient’s condition and the stage of pregnancy.

Treatment methods for thyroid nodules in pregnancy

The treatment method for thyroid nodules during pregnancy depends on the patient’s condition, the number, size, and whether the nodules are benign or malignant. Below, we will introduce the treatment methods for thyroid nodules and explain which ones are allowed during pregnancy.

Regular monitoring

Treatment of thyroid nodules during pregnancy often involves monitoring the nodule, since most nodules are benign at this time. However, postpartum surveillance is also necessary, as hormonal changes of pregnancy can affect nodules. The timing of postpartum consultation should be determined with the patient’s agreement and based on the results of ultrasound or cytology. If the results indicate a possible malignancy, specialist consultation is recommended within 6 months of delivery. Overall, decisions about how to manage a nodule should be made with the active participation of the patient and based on the available evidence.

Toxic thyroid nodule

In the presence of a toxic thyroid nodule before pregnancy with a TSH level of less than 0.1 mIU/L, pre-pregnancy treatment is the priority. In the first trimester of pregnancy, treatment with beta-blockers can be initiated for symptomatic cases. Treatment with antithyroid drugs (ATDs) is rarely necessary and the decision should be made after assessing the benefits and risks (i.e., complications of hyperthyroidism during pregnancy versus complications of ATDs). Complications of ATDs with propylthiouracil (PTU) are fewer than with other ATDs. Since ATDs cross the placenta, if ATD treatment is continued into the second trimester (fetal thyroid becomes active from week 18 of pregnancy), the goal of treatment is to maintain maternal Free T4 in the upper normal range to prevent fetal hypothyroidism. In these cases, fetal ultrasound monitoring should be performed from week 22 onwards to check for signs of fetal hypothyroidism (goiter). Iodine supplements are not recommended in this situation, and the use of radioactive iodine is contraindicated during pregnancy. In cases of symptomatic hyperthyroidism, symptomatic treatment (beta blockers) is prescribed as the first line of treatment, and treatment with ATDs at the minimum effective dose (target Free T4 in the upper normal range) is necessary in rare cases.

Suppressive therapy

Suppressive therapy involves the use of the drug levothyroxine (L-thyroxine). This treatment, which is used to reduce the size of benign thyroid nodules, is generally not recommended during pregnancy. Because during pregnancy, the risk of complications from increased thyroid hormone in the blood (hyperthyroxinemia) is higher for the mother and fetus. Therefore, the use of levothyroxine for the treatment of thyroid nodules during pregnancy is prohibited.

Thermal ablation of thyroid nodules

This method involves the use of heat (for example, radiofrequency) to destroy the nodule tissue. There is insufficient information about the safety and side effects of this treatment during pregnancy. In other words, it is not known what effect this method has on the mother and fetus. Due to the lack of sufficient data and the contraindications to the use of radiofrequency, doctors currently do not recommend thermal ablation of the thyroid during pregnancy.

Thyroid microcarcinoma (slow-growing cancerous thyroid nodule)

If small thyroid nodules with the possibility of papillary cancer (microcarcinoma) are diagnosed before or during pregnancy, active surveillance is recommended if there is no lymph node involvement. Surgery during pregnancy is not recommended for these types of cancers, which are usually slow-growing. If the cancer progresses during pregnancy, the decision to have surgery or continue monitoring should be made by a multidisciplinary medical team.

Surgery

Thyroid surgery during pregnancy is not recommended for benign or stable nodules; however, in cases of suspicious nodules or nodules that put pressure on surrounding structures, it can be performed after examination by a multidisciplinary team. The best time for surgery is the second trimester of pregnancy; because the first trimester increases the risk of miscarriage and the third trimester increases the risk of preterm labor. Surgery is allowed at any stage of pregnancy if the mother’s life is threatened. Thyroid cancer without lymphatic metastasis or invasive features usually does not require urgent surgery during pregnancy; however, if the tumor progresses or has invasive features, surgery is recommended in the second trimester. If surgery is deemed necessary in the second or third trimester of pregnancy, it should be postponed until after delivery and postpartum follow-up should be carefully planned.

Effect of thyroid nodules in pregnancy

Thyroid nodules during pregnancy can have different effects. Benign nodules that do not interfere with normal thyroid function usually do not directly affect pregnancy. However, functional nodules (hyperthyroidism or hypothyroidism) can cause serious complications. Untreated hyperthyroidism may lead to miscarriage, premature birth, preeclampsia, and heart failure in the mother. Untreated hypothyroidism can also cause miscarriage, premature birth, fetal neurodevelopmental problems, and anemia in the mother. Thyroid cancer is rare in pregnancy; however, when present, it requires careful management.

The Bottom Line

During pregnancy, several factors can contribute to the development and growth of benign or malignant thyroid nodules. These include iodine deficiency, the stimulatory effect of hCG on TSH receptors, and increased TSH and estrogen. Proper diagnosis and management of thyroid nodules before and during pregnancy is very important. Pregnant women with thyroid nodules should be monitored by an endocrinologist and gynecologist and have regular thyroid tests to assess gland function and adjust the dosage of thyroid medications.