Impact of Pregnancy on Outcome and Prognosis of Survivors of Papillary Thyroid Cancer

Abstract

Background:

Papillary thyroid cancer (PTC) commonly affects women of child-bearing age. During normal pregnancy, several factors may have a stimulatory effect on normal and nodular thyroid growth. The aim of the study was to determine whether pregnancy in thyroid-cancer survivors poses a risk of progression or recurrence of the disease.

Methods:

The files of 63 consecutive women who were followed at the Endocrine Institute for PTC in 1992–2009 and had given birth at least once after receiving treatment were reviewed for clinical, biochemical, and imaging data. Thyroglobulin levels and neck ultrasound findings were compared before and after pregnancy. Demographic and disease-related characteristics and levels of thyroid-stimulating hormone (TSH) during pregnancy were correlated with disease persistence before conception and disease progression during pregnancy using Pearson's analysis.

Results:

Mean time to the first delivery after completion of thyroid-cancer treatment was 5.08 ± 4.39 years; mean duration of follow up after the first delivery was 4.84 ± 3.80 years. Twenty-three women had more than one pregnancy, for a total of 90 births. Six women had evidence of thyroid cancer progression during the first pregnancy; one of them also showed disease progression during a second pregnancy. Another two patients had evidence of disease progression only during their second pregnancy. Mean TSH level during pregnancy was 2.65 ± 4.14 mIU/L. There was no correlation of disease progression during pregnancy with pathological staging, interval from diagnosis to pregnancy, TSH level during pregnancy, or thyroglobulin level before conception. There was a positive correlation of cancer progression with persistence of thyroid cancer before pregnancy and before total I-131 dose was administered.

Conclusions:

Pregnancy does not cause thyroid cancer recurrence in PTC survivors who have no structural or biochemical evidence of disease persistence at the time of conception. However, in the presence of such evidence, disease progression may occur during pregnancy, yet not necessarily as a consequence of pregnancy. The finding that a nonsuppressed TSH level during pregnancy does not stimulate disease progression suggests that it may be an acceptable therapeutic goal in this setting.

Introduction

D ifferentiated epithelial thyroid cancer (DTC) is approximately thrice more frequent in women than men and commonly occurs in women of child-bearing age (1). Papillary thyroid cancer (PTC) is the most common histotype, accounting for nearly 80% of cases. In the United States, DTC is the sixth most common malignancy diagnosed in women aged 20–49 years and the second most common tumor diagnosed during pregnancy, with a prevalence of 14 per 100,000 deliveries (2,3). These observations have led some authors to speculate that the development of thyroid cancer may be triggered by the hormones of pregnancy. During normal pregnancy, the first-trimester increase in human chorionic gonadotropin as well as the increased concentration of estrogens are known to have stimulatory effects on the thyroid gland (4). The thyroid gland may undergo a 20% to 30% increase in volume during pregnancy; thyroglobulin (Tg) levels are approximately 25% higher in the third trimester than in the first year postpartum. It is also well accepted that thyroid nodules grow during pregnancy. Kung et al. (5) showed that pregnancy both promotes existing thyroid nodules and induces the formation of new ones.

Since pregnancy appears to stimulate normal and nodular thyroid growth in healthy women, it is reasonable to be concerned that in women with thyroid cancer, pregnancy may stimulate thyroid cancer cell growth leading to thyroid cancer recurrence or progression. Several authors have examined the management and prognosis of DTC diagnosed during pregnancy (6 –9), with discordant results. Although some reported no significant impact of pregnancy on outcome (6 –8), a very recent study using the new international guidelines for persistence/relapse assessment reached the opposite conclusion (9). However, very few studies of the potential impact of pregnancy on thyroid cancer have been conducted in thyroid-cancer survivors. In 1965, Rosvoll and Winship (10) noted no recurrence of thyroid cancer during or after pregnancy in 38 women who had been disease free for 2–15 years before conception. One year later, Hill et al. (11) reported similar recurrence rates between 70 survivors of thyroid cancer who became pregnant after diagnosis and 109 women with thyroid cancer who did not. Since these investigations were conducted, however, the paradigm for disease detection in low-risk survivors has shifted from routine diagnostic whole-body radioactive iodine scanning to a greater reliance on neck ultrasonography and serum Tg determinations. In a single more recent study on the subject, Leboeuf et al. (12) compared structural imaging findings and serum Tg levels before pregnancy and shortly after delivery in 36 survivors of thyroid cancer. They concluded that pregnancy is unlikely to cause clinically significant disease recurrence in the early postpartum period when structural imaging confirms the absence of residual disease, but it may occasionally be associated with progression of known metastatic lesions. The authors suggested that studies of larger samples with longer follow up were warranted to corroborate their findings.

Thus, the aim of the present study was to determine whether pregnancy in survivors of thyroid cancer poses a risk of progression or recurrence of the disease. We evaluated a fairly large group of 63 survivors of thyroid cancer who gave birth to 90 children after initial treatment and were followed for a median of nearly 4 years after delivery. We analyzed their demographic, clinical, biochemical, and imaging data, including repeated measurements of thyroid-stimulating hormone (TSH) during pregnancy. We also compared Tg levels and sonographic findings before and after pregnancy to identify signs of disease progression during pregnancy and correlated the results with demographic parameters, disease-related indices, and TSH levels during pregnancy.

Materials and Methods

A retrospective case-series design was used. The study group consisted of all consecutive women who were followed at the Endocrine Institute of Rabin Medical Center for PTC from 1992 to 2009 and had given birth at least once after receiving thyroid-cancer treatment. The medical records were reviewed for age at diagnosis of thyroid cancer and at delivery, pathological tumor-node-metastasis (TNM) staging of the thyroid cancer according to the American Joint Committee on Cancer (sixth edition), type of thyroid cancer treatment (thyroidectomy, lobectomy, radioactive iodine, repeated surgeries, and repeated radioactive iodine treatments), levels of Tg before and during pregnancy and within 1 year after delivery, and levels of TSH during pregnancy. We also documented the results of structural imaging studies, mostly neck ultrasound, before and after pregnancy and the most recent one available.

Each patient was categorized by thyroid cancer status before pregnancy: free of disease, defined as a Tg level below 0.9 ng/mL on L-thyroxine treatment with negative anti-Tg autoantibodies and neck ultrasound; or persistent disease, defined as at least one of the following findings: detectable Tg level (above 0.9 ng/mL) on L-thyroxine treatment, neck mass on imaging with positive cytology for metastasis of thyroid cancer or radioiodine uptake outside the thyroid bed; persistent anti-Tg antibodies with a consistent trend to increase. To determine thyroid cancer progression or recurrence during pregnancy, we compared prepregnancy and postpregnancy (within 1 year after delivery) Tg levels on L-thyroxine treatment and neck ultrasound findings. In the presence of serum anti-Tg antibody, which precluded accurate measurements of serum Tg, we recorded the antibody titers during follow up.

Thyroid cancer progression during pregnancy was defined as a finding of one or more of the following criteria: 20% or more increase in serum Tg from the prepregnancy level, consistent increase of 20% or more in serum anti-Tg antibodies during pregnancy (based on the concept that an increase in antibody production depends on an increase of autoantigen in the body), a new metastatic lesion on neck ultrasound performed within 1 year after delivery, or an increase in size of a prepregnancy lesion on neck ultrasound.

Disease persistence before conception and the presence or absence of disease progression during pregnancy were analyzed against the demographic parameters, disease-related indices, and TSH levels during pregnancy.

In cases of more than one pregnancy, all pregnancies were included in the analysis. However, the data for the first pregnancy were separately analyzed from the data for the subsequent one to explore the significance of repeated pregnancies on the natural history of thyroid cancer.

The study was approved by the Institutional Review Board.

Laboratory measurements of TSH and TG

TSH was determined by a solid-phase, two site chemilumunescent immunometric assay, run on Immulite 2000 (Siemens Medical Solutions Diagnostics, Los Angeles, CA).

Tg was determined by a solid-phase, chemiluminescent immunometric assay, run on Immulite 2000 (CRM 457, molecular mass 660 kDa; Siemens Medical Solutions Diagnostics). The assay exhibits an analytical sensitivity of 0.2 ng/mL and a functional sensitivity of 0.9 ng/mL, cv 4.8–6.8%.

In women in whom Tg level was measured before 2000, any level below the assay detection limit was defined as 0.

Statistical analysis

The relationships of disease stage with disease persistence before pregnancy and with disease progression during pregnancy were analyzed using Spearman's correlation coefficient. The relationship between disease progression during pregnancy and disease persistence before conception was analyzed by Fisher's exact test (χ ² test for independent samples was not applicable because of the low expected counts.) The relationships of the clinical characteristics with disease persistence before conception and with disease progression during pregnancy were analyzed using Pearson's correlation (in this case, equivalent to the independent samples t-test).

Results

Clinical characteristics

Sixty-three women met the inclusion criteria. All were younger than 45 years at diagnosis. Thyroid-cancer treatment consisted of total thyroidectomy in 59 women, of whom 58 (98.3%) underwent subsequent radioactive iodine remnant ablation (RRA), and hemithyroidectomy in 4 women, none of whom was treated by RRA. Forty women gave birth to 1 child after treatment, 19 gave birth to 2, and 4 gave birth to 3, for a total of 90 deliveries. The mean (±SD) interval from treatment to the first delivery was 5.08 ± 4.39 years (median 3.20 years). The mean duration of follow up after the first delivery was 4.84 ± 3.80 years (range, 3 months to 17.3 years; median 3.75 years). The demographic, clinical, histopathological, and biochemical features of the patients during the first pregnancy are shown in Table 1.

Table 1.

Demographic, Clinical, Histopathological, and Biochemical Features of 63 Thyroid-Cancer Survivors During Their First Pregnancy

Characteristic	Value
Maternal age at delivery (years)
Mean ± SD	29.7 ± 4.7
Median	29.41
Range	20.1–41.2
Age at diagnosis of thyroid cancer (years)
Mean ± SD	24.7 ± 5.8
Median	25
Range	10–38
pTMN—T stage at diagnosis
T1	30 (47.6)
T2	11 (17.5)
T3	17 (27)
T4	1 (1.6)
Missing data	4 (6.3)
pTMN—nodal involvement at diagnosis
Nx/No	30 (47.6)
N1	31 (49.2)
N1a	16
N1b	12
Not determined	3
Missing data	2 (3.2)
pTMN—metastases at diagnosis
M0	59
M1	2
Missing data	2
Total I-131 dose (mCi)
Mean ± SD	185 ± 152
Median	150
Range	0–750
First TSH level in pregnancy (mIU/L)
Mean ± SD	1.66 ± 3.71
Median	0.27
Range	0–22.8
Number of TSH tests during pregnancy
Mean	4.87
Median	5
Std deviation	2.27
Range	1–8
Average TSH level in pregnancy (mIU/L)
Mean ± SD	2.65 ± 4.14
Median	1.2

pTNM, pathological tumor-node-metastasis; TSH, thyroid-stimulating hormone.

Persistent disease before the first pregnancy

Thirteen women (20.6%) were categorized as having persistent PTC before conception. Their clinical data, Tg levels, and imaging findings before and after pregnancy are presented in Table 2. Five of these women underwent lymph node dissection after initial surgery before conception (patient nos. 1, 2, 8, 11, and 12 in Table 2).

Table 2.

Patients with Thyroid Cancer Persistence Before Conception

				Tg level (ng/mL)		Neck imaging
Pt. no.	Age at diagnosis (years)	Staging pTMN	Total I131 administered before pregnancy (Total during follow-up) (mCi)	Before pregnancy	After delivery	Before pregnancy	After delivery ^a	Cancer progression
1	24.5	T4N1M0	350 (350)	23.9	21.4	Negative	Negative	No
2	23	T1N1M0	410 (410)	9.1	9.5	Positive	New findings 5 months postpartum:	Yes
3	22	T2N1M0	150 (300)	1.3	0.7	Negative	Negative	No
4	24.7	T3N0M0	180 (330)	0	1.7	Positive	Stable.	Yes
5	23	T3N1M0	150 (500)	8.2	6.0	Negative	Negative	No
6	28	T3N1M0	100 (450)	5.0	5.4	No details	No details	No
7	18	NA	300 (300)	4.7	4.5	Negative	Negative	No
8	25	T3N1M0	450 (450)	7.2	6.9	Positive	Stable	No
9	27	T1N0M0	150 (150)	0	0	Positive	New finding + growth of a prepregnancy finding 1 month postpartum	Yes
10	27.3	T3N0M0	100 (250)	NA	NA	Not done	Findings 5 + 6 mm 4 month postpartumpapillary thyroid cancer per FNA	Yes
11	15.6	T1N1M0	255 (255)	0	0	Positive	Growth of prepregnancy finding 3 months postpartum	Yes
12^b	30.4	T3N1M0	500 (500)	Tg antibodies	Tg antibodies	Negative	Negative	Yes
13	17.1	T2N1M0	100 (250)	NA	NA	Positive	Stable	No

Within a year after giving birth—postpartum.

Patient had an increase in anti-Tg antibodies.

Tg, thyroglobulin; NA, not available.

Twelve patients were categorized as having persistent disease on the basis of a detectable Tg level on L-thyroxine treatment and/or neck imaging findings. Patient 10 was unique in that she conceived 3 months after RRA and did not undergo neck ultrasound or blood measurements of Tg until 4 months after delivery, when pathological lymph nodes were detected. Due to the unusual temporal proximity of the initial treatment for PTC, the pregnancy, and the finding of metastatic lymph nodes, we included her in the group of patients with persistent disease.

Serum Tg levels

All Tg data included in the analysis pertained to measurements made on L-thyroxine treatment. The values of the four patients treated by hemithyroidectomy and the seven women who had Tg antibodies were excluded. We also excluded five women for whom pre- or postpregnancy data were missing.

In the remaining 47 women, the mean (±SD) Tg level before the first pregnancy was 1.23 ± 3.93 ng/mL (range 0–23.9 ng/mL), and the mean postpartum level was 1.18 ± 3.54 ng/mL (range 0–21.4 ng/mL). The difference was not statistically significant.

In 39 of the 47 women (82.9%), a Tg level below 0.9 ng/mL was documented both before and after the first pregnancy. The data for the other 8 women are presented in Table 2 (nos. 1–8). In this subgroup, there was no significant change in Tg level from before pregnancy to after delivery (mean suppressed Tg, 7.42 + 7.37 ng/mL and 7.01 ± 6.44 ng/mL, respectively), with similar TSH suppression (0.17 ± 0.41 mIU/mL before pregnancy, 0.1 ± 0.13 mIU/mL after delivery). In seven of the eight women, Tg was detectable before and after pregnancy, and in only one (patient 4) was Tg undetectable before pregnancy and rose postpartum to detectable levels (1.7 ng/mL). The latter patient was, therefore, categorized as having thyroid cancer progression during pregnancy.

One additional woman (patient 2) among those who had a detectable Tg level before pregnancy was considered to have thyroid cancer progression during pregnancy due to a metastatic lymph node detected 5 months postpartum.

Structural evidence of disease

Data on the neck ultrasound examination after diagnosis of thyroid cancer (before the first pregnancy) were available for 56 women. Fifty had no suspicious sonographic findings. The data for the other 6 women are presented in Table 2 (serial nos. 2, 4, 8, 9, 11, and 13). In 4 of these patients (nos. 2, 9, 11, 13), fine-needle aspiration study revealed PTC cells, and in 2 patients (nos. 4, 8) pathological I-131 uptake was noted at the location of the sonographic lesion outside the thyroid bed. In 2 of the 6 women (nos,. 2, 8), Tg level before pregnancy on L-thyroxine treatment was above 0.9 ng/mL; in 3 (nos. 4, 9, 11) women, it was below 0.9 ng/mL; and in 1 (no. 13) woman, the Tg level was missing.

None of the patients with a normal prepregnancy neck ultrasound scan had new abnormal sonographic findings after delivery. Of the six women with abnormal prepregnancy neck ultrasound findings, one (serial no. 2) had a new lymph node metastases 5 months postpartum; one patient (serial no. 9) had both a new lesion and growth of a preexisting pathological lymph node 1 month postpartum; and one woman (no. 11) showed growth of a preexisting pathological lymph node 3 months postpartum.

Patient 10, as mentioned above, did not undergo neck ultrasound during the 3 months between RRA and conception. However, given the absence of lesions suggesting lymph node metastases from both the preoperative ultrasound scan and the pathological specimen, we defined her status as probable progression during pregnancy.

For the statistical analysis, due to their small number, we categorized the four women with definite aggravation and the sole woman with probable aggaravation as having thyroid cancer progression.

Serum TSH during the first pregnancy

Serum TSH measurements during the first pregnancy after diagnosis of DTC were available in 58 of 63 women (92%). In 52 of them (89.6%), the first TSH measurement was done in the first trimester, and in the remaining 6, in the second trimester. In most of the participants, TSH level was measured several times during pregnancy (median five times). The mean value was 2.65 ± 4.14 mIU/L (median 1.20 mIU/L), well above the recommended level for pregnant women who survived thyroid cancer. Only in eight women (12.6%) was the TSH level below 1 mIU/L throughout the first pregnancy. In 19 women (30.1%), at least one measurement was above 5 mIU/L during the first pregnancy. However, no correlation was found between TSH level and disease progression or Tg level during pregnancy.

Thyroid cancer progression during pregnancy

Overall, six patients out of the 63 (9.5%) were categorized as having thyroid cancer progression during their first pregnancy after diagnosis of thyroid cancer. In four patients (nos. 2, 9, 10, and 11), the categorization was based on a new finding or worsening of a preexisting finding on neck ultrasound performed within a year after delivery combined with a positive cytology for PTC. In patient 4, it was based on the elevation in Tg level postpartum, and in patient 12, it was based on the consistent increase in Tg antibodies throughout the follow-up period, including pregnancy (Table 2).

Correlation of demographic and clinical factors with disease persistence before pregnancy/disease progression during pregnancy

Thyroid cancer persistence before pregnancy was significantly correlated with tumor size and extension (T in pathological TNM staging; p = 0.001, r = 0.345). It was also correlated with total I-131 administered both until conception and during the whole follow-up period: Women with persistent disease before pregnancy received 243.46 ± 143.63 mCi until conception, whereas women with no evidence of disease before pregnancy received 99.77 ± 69.23 mCi. The mean total amount of I-131 administered during the whole follow-up period was 345.8 ± 109.1 mCi in the women with persistent disease and 115.4 ± 87.3 in the women with no prepregnancy evidence of disease (p < 0.001, r = 0.729). Disease persistence was also correlated with Tg level before pregnancy (p < 0.001, r = 0.606). No significant correlation was found between disease persistence and the other parameters measured.

Regarding disease progression during pregnancy, we found no statistically significant correlation with the following parameters: patient age at diagnosis of thyroid cancer, patient age at delivery, interval from diagnosis of thyroid cancer to pregnancy, pathological TNM staging of thyroid cancer, mean, median, or maximal TSH level during pregnancy, and Tg level before conception. There was a strong positive correlation between persistence of thyroid cancer before pregnancy and cancer progression during pregnancy (χ ²(1) = 23.17, p < 0.001, Cramer's V = 0.632): Every one of the six patients with thyroid cancer progression during pregnancy had evidence of PTC persistence before conception. We also found a strong positive correlation of total I-131 dose administered both until pregnancy and during the whole follow-up period with thyroid cancer progression during pregnancy: The total dose until conception measured 260 ± 161.19 mCi in the women with PTC progression and 123.5 ± 96.22 mCi in those without progression (r = 0.376, p = 0.003); the total dose during the whole follow-up period was 315.83 ± 125.3 and 157.5 ± 126.68, respectively (p = 0.005, r = 0.357).

Thyroid cancer progression during second pregnancy

Twenty-three women gave birth twice or more after thyroid cancer treatment. The thyroid cancer progressed during the second pregnancy in three women. These patients had documented disease persistence before both the first and the second pregnancies. In one of them (patient no. 12, Table 2), thyroid cancer progressed during both the first and the second pregnancies, and in two (patient nos. 5, 8), only during the second. Four women gave birth thrice after PTC diagnosis and treatment. Disease progression did not occur in any of these third pregnancies.

Patients' current status

Eleven of the 13 patients who were categorized as having persistent disease before the first pregnancy (nos. 1, 2, 5–13) still had biochemical and/or structural evidence of PTC persistence at the last follow up. Six of them (nos. 1, 5, 6, 9, 10 and 13) have received additional treatment for their disease since giving birth: Patients 1 and 9 underwent lymph node dissection; patient 10 received additional I-131 (150 mCi); and patients 5, 6, and 13 underwent surgery and received additional I-131 (150–350 mCi). In addition, patients 3 and 4 received additional I-131 treatment (150 mCi) postpartum and currently have no evidence of PTC.

Discussion

DTC may recur or persist in up to 20% of treated patients, even many years after initial therapy. Early detection and treatment of recurrent disease is assumed to lower morbidity and prolong life and is, therefore, the primary goal of follow up in survivors of thyroid-cancer (13). The present study shows that pregnancy is not a risk factor for PTC recurrence in women with a negative prepregnancy ultrasound scan and undetectable Tg/Tg antibody levels on L-thyroxine treatment. However, when there is evidence of persistent disease before a first posttreatment pregnancy, especially a structural finding, the risk of disease progression during pregnancy is significant (6/13 patients in the present study). Our finding agrees with the study by LeBouef et al. (12), which explored the impact of pregnancy in 36 survivors of thyroid cancer who were followed for a median of 4 months after delivery. However, in the present study, the cohort was larger, and the vast majority of the women were similarly treated with total thyroidectomy and RRA and regularly followed by frequent Tg measurements and ultrasound examinations for a median of almost 4 years after delivery. We found that in those patients who showed thyroid cancer progression, either biochemically or radiologically, the natural history of the cancer was already more aggressive before pregnancy than in the rest of the group, as reflected by their need for repeated radioactive iodine treatments. Thus, although pregnancy may have served as a mild stimulus for the thyroid cancer in these cases, it seems more reasonable to explain the cancer's progression by the natural history of the disease alone. It is noteworthy that none of the patients had macroscopic palpable neck disease or distant metastasis after initial therapy during follow up.

Although the study group was not homogenous in terms of tumor size and local extension (46% had T2, T3, or T4 tumors) or lymph node metastasis (47.6%), and despite the strong correlation between the tumor characteristics (T in the pathological TNM staging) and disease persistence before conception, there was no correlation between the initial pathological staging and disease progression during pregnancy. Several systems for thyroid cancer staging and risk stratification have been published, and each provides an estimation of prognosis. However, on follow up, additional data are accumulated that may either upgrade or downgrade the initial evaluation. Some authors refer to the integration of predictive values based on these additional data as “ongoing risk stratification” (14). Although the pathological staging of DTC is associated with both the cancer cell characteristics and the time to diagnosis, the data collected during follow up may reflect the tumor behavior and response of the cancer cells to therapy. In our study, which involved mainly low-risk patients, the ongoing risk stratification proved more relevant than the initial staging for predicting thyroid cancer progression during pregnancy. The need for repeated radioactive iodine treatments is an indicator of aggressive tumor behavior and, possibly, relative resistance of the cancer cells to iodine, which may result in their proliferation and growth during pregnancy.

According to the Endocrine Society guidelines for the treatment of thyroid dysfunction during pregnancy (15), it is reasonable to use the same guidelines outside of pregnancy to determine the degree of TSH suppression according to whether the woman has evidence of persistent disease (<0.1 mIU/L) or appears clinically free of disease (0.1–0.5 mIU/L). In our study, TSH suppression was not achieved in the majority of participants despite the frequent TSH measurements during pregnancy: In approximately 90% of the pregnancies analyzed, TSH level was measured at least once, and the median number of measurements was 5, enabling frequent L-thyroxine dose adjustments. Alexander et al. (16) found that levothyroxine requirements increased as early as the fifth week of gestation, with a median time of 8 weeks' gestation. Apparently, in the present study, the dose adjustment did not meet this early increased requirement. Twenty-two of the 58 women (39.6%) for whom data on TSH level during the first trimester were available had a TSH level above 0.5 mIU/L, and in 11 women (18.9%), the TSH level was above 3 mIU/L. Similar results for first-trimester TSH were reported in previous studies on hypothyroid women receiving thyroxine replacement, with no history of thyroid cancer (17,18). Nevertheless, we found no correlation between TSH level during pregnancy and disease progression. Although a nonsuppressed TSH level is believed to stimulate the growth of residual thyroid cells, some authors believe that in patients at low risk of thyroid cancer, no significant improvement can be achieved by suppressing TSH, such that the goal of L-thyroxine treatment should be a normal-range TSH level (0.5–2.5 mU/L) (19). Given the fetal and neonatal risks of maternal hyperthyroidism, this is especially relevant in women at high risk of obstetrical complications (20,21).

In summary, our study confirms that pregnancy does not have an impact on disease recurrence in survivors of thyroid cancer without evidence of disease persistence before conception. A nonsuppressed TSH level during pregnancy does not seem to cause disease progression and may be acceptable, especially in women with previous obstetrical or fetal complications.

Footnotes

Disclosure Statement

The authors declare that no competing financial interests exist.

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