During the early stages of most clinical trials, medical researchers tend to recruit healthy adult males with no comorbidities. This is because they generally represent the safest segment of the population for experimental therapies to be tested on. In contrast, women of reproductive age tend to be the last segment of the population to be recruited for clinical trials due to potential concerns about the safety of the fetus if the woman is pregnant or becomes pregnant during the study. 

Pregnancy entails massive biological changes to a woman’s body. There is often a separate protocol for most things in medicine for pregnant women and women of reproductive age. In reality, however, some physicians may not be fully aware of the separate diagnostic and treatment guidelines for this group of patients.

In Endocrinology and Metabolism Clinics of North America, van Velsen and colleagues wrote about the specific diagnostic and treatment considerations for thyroid cancer in women of reproductive age and the perinatal period. From the very onset, they highlighted that thyroid cancer occurs more frequently in women compared to men.

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“Thyroid cancer . . . is one of the most common cancers diagnosed in women of reproductive age. It is estimated to make up 20% of all diagnosed cancers in the perinatal period,” they wrote. 

Read more about medullary thyroid carcinoma etiology 

In addition, the global incidence of thyroid cancer has been rising steadily for the last 20 years. The most common thyroid cancers remain differentiated thyroid cancers, such as papillary and follicular thyroid carcinomas; these cancers represent 80% to 85% of all thyroid cancers. Anaplastic and medullary thyroid carcinomas make up the remaining 20%. 

A Bidirectional Relationship?

Let’s examine 2 key points: the impact of pregnancy on thyroid cancer, and the impact of thyroid cancer on pregnancy. In the first case, it is important to understand that the typical physiological changes that occur in pregnancy may complicate normal thyroid test results. The thyroid gland is known to increase by 10% in iodine-replete areas; in iodine-deficient areas, it is known to increase by 20% to 40%. In addition, serum thyroglobulin concentrations naturally increase during pregnancy.

The notion that pregnancy promotes the growth of existing thyroid cancer has been speculated by some. However, repeated studies have made clear that pregnancy does not promote thyroid cancer growth to a clinically meaningful extent. In addition, studies have demonstrated that overall and disease-free survival are not impacted by pregnancy in newly diagnosed cases of differentiated thyroid cancer.

Making the Decision to Start a Family, Despite MTC

As for the impact of thyroid cancer on pregnancy, studies on general cancer survivors reveal that cancer raises the risk of adverse pregnancy outcomes, such as preterm birth. This has also been attributed to the long-term effects of chemotherapy.

However, it is difficult to conduct clinical studies of a prospective nature, given the relatively rare occurrence of thyroid cancer in women of reproductive age. Studies indicate that malignancy is neither an absolute indication for a Cesarean section nor an absolute risk for preterm birth. 

Van Velsen and colleagues wrote, “Clear communication and reassurance regarding similar risks of adverse pregnancy outcomes are important in this population, as young women in particular exhibit more distress and anxiety related to a thyroid cancer diagnosis, which are independent risk factors for adverse pregnancy outcomes.” 

Diagnosis During Pregnancy

In the Saudi Journal of Anaesthesia, Muzannara and colleagues presented the case of a patient who was diagnosed with medullary thyroid carcinoma, among other diseases, while pregnant. 

The patient (gravida 4, para 1) presented at 22 weeks gestation complaining of severe headache. Upon examination, the patient was found to be hypertensive and tachycardic. Test results revealed that she had pheochromocytoma. 

Additional laboratory investigations revealed high levels of parathormone (8.7 pmol/L) and calcitonin (325 pg/mL). This indicated hyperparathyroidism. Scans revealed a 3.5 cm x 3.1 cm cystic mass on the left adrenal gland, thyroid nodules with bilateral cervical lymph nodes, and multiple adenomatoses of parathyroid glands. Fine needle aspiration confirmed the diagnosis of medullary thyroid carcinoma. The patient’s final diagnosis was MEN 2A, or Sipple’s syndrome. 

Read more about medullary thyroid carcinoma treatment 

The patient was advised to undergo a total thyroidectomy for the medullary thyroid carcinoma but she refused. She later presented for labor at 39 weeks gestation. She successfully delivered a healthy 7.5 lb boy with forceps assistance. 

In this case study, the patient was diagnosed with thyroid cancer in the middle of her pregnancy. However, despite refusing surgery, the cancer did not have a substantial effect on her pregnancy as she only returned to the hospital for delivery. 

In the midst of ensuring that pregnant women with thyroid cancers are properly cared for, it is important to not neglect the psychological aspects of having to go through pregnancy and cancer simultaneously.

“A new cancer diagnosis is always challenging for a patient and their family to process. It may be particularly so during pregnancy,” Sullivan wrote in Clinical Obstetrics and Gynecology. “Careful counseling and supportive care is needed This is a situation where a multidisciplinary team can provide both reassurance to the patient and optimal outcome.” 


van Velsen EFS, Leung AM, Koreevar TIM. Diagnostic and treatment considerations for thyroid cancer in women of reproductive age and the perinatal period. Endocrinol Metab Clin North Am. Published online May 4, 2022. doi:10.1016/j.ecl.2021.11.021

Sullivan SA. Thyroid nodules and thyroid cancer in pregnancyClin Obstet Gynecol. 2019;62(2):365-372. doi:10.1097/GRF.0000000000000431

Muzannara MA, Tawfeeq N, Nasir M, Al Harbi MK, Geldhof G, Dimitriou V. Vaginal delivery in a patient with pheochromocytoma, medullary thyroid cancer, and primary hyperparathyroidism (multiple endocrine neoplasia type 2A, Sipple’s syndrome)Saudi J Anaesth. 2014;8(3):437-439. doi:10.4103/1658-354X.136652