Progesterone use may be linked to increased risk of thyroid cancer, study finds

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.

A recent retrospective study of more than 140,000 infertile women in Denmark found that women who used progesterone had an approximately 60% increased risk of developing thyroid cancer compared to women who had never used progesterone, but the overall risk was very high.
low (0.
12%)
.

The researchers conducted a population-based retrospective study of 146,024 infertile women aged 20 to 45 years living in Denmark between 1995 and 2017
.

Participants were followed until thyroid cancer, any other cancer, death, immigration, total thyroidectomy, or until the end of the follow-up period on December 31, 2018
.

Of this cohort, 88.
6% used fertility drugs during the study period, and 167 were diagnosed with thyroid cancer
.

The median time from infertility diagnosis to thyroid cancer diagnosis was 9.
1 years
.

Of those diagnosed with thyroid cancer, 84% had papillary thyroid cancer and 13% had follicular thyroid cancer
.

Thyroid cancer risk was significantly higher in progesterone-experienced patients.
After adjustment for time at study start, education level, parity, obesity, thyroid disease, and history of hormonal contraception, no clomiphene citrate use, human Increased risk of thyroid cancer in women on chorionic gonadotropin, gonadotropin, and gonadotropin-releasing hormone receptor modulators
.

However, women using progesterone had a significantly increased risk of any thyroid cancer (aHR=1.
63; 95%CI, 1.
07-2.
48) and papillary thyroid cancer (aHR=1.
66; 95%CI, 1.
04-2.
65)
.

Thyroid cancer rates are low overall, and the study is the largest to date in the field, the researchers wrote
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The data from the study further add to current concerns about a potential link between fertility drugs and thyroid cancer
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However, both women who had taken progesterone and women who had never taken progesterone had lower rates of thyroid cancer overall
.

Moreover, due to the existence of confounding factors, it cannot be ruled out that this conclusion is due to accidental factors, and more research is needed to explore in the future
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Compiled and edited by: Sofie Lindquist, Susanne K Kjær, Vanna Albieri, Kirsten Frederiksen, Tatiana Hansen, Bugge Nøhr, Allan Jensen, Fertility drugs and incidence of thyroid cancer in a Danish nationwide cohort of 146 024 infertile women, Human Reproduction, Volume 37, Issue 4, April 2022, Pages 838–847, https://doi.
org/10.
1093/humrep/deab285