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Levothyroxine treatment is associated with an increased relative risk of overall and organ specific incident cancers – a cohort study of the Swedish population

Wändell, Per LU ; Carlsson, Axel C. ; Li, Xinjun LU ; Sundquist, Jan LU and Sundquist, Kristina LU (2020) In Cancer Epidemiology 66.
Abstract

High thyroid hormone values have been associated with an increased risk of incident cancers, especially breast cancer but also lung cancer and any solid cancers. We explored whether there is an increased risk of overall and cause-specific cancers in those receiving levothyroxine treatment. We included all individuals ≥ 18 years in Sweden (N = 8,573,313) on January 1 2009, and identified patients with two or more dispensed prescriptions of levothyroxine 2005–2006 (n = 253,193, 3.0 %). A cancer diagnosis in the Swedish Cancer Register 2009–2015 was used as outcome. We excluded patients with a cancer diagnosis before 2005. Cox regression was used (hazard ratios, HRs, and 95 % confidence intervals, CI) with adjustments for age,... (More)

High thyroid hormone values have been associated with an increased risk of incident cancers, especially breast cancer but also lung cancer and any solid cancers. We explored whether there is an increased risk of overall and cause-specific cancers in those receiving levothyroxine treatment. We included all individuals ≥ 18 years in Sweden (N = 8,573,313) on January 1 2009, and identified patients with two or more dispensed prescriptions of levothyroxine 2005–2006 (n = 253,193, 3.0 %). A cancer diagnosis in the Swedish Cancer Register 2009–2015 was used as outcome. We excluded patients with a cancer diagnosis before 2005. Cox regression was used (hazard ratios, HRs, and 95 % confidence intervals, CI) with adjustments for age, socioeconomic/neighborhood factors and co-morbidities. Totally 399,751 cases of incident cancer were identified, with a slight increased overall risk associated with levothyroxine treatment for both men, adjusted HR 1.06 (95 % CI 1.03–1.10), and women, adjusted HR 1.08 (95 % CI 1.07–1.10). For men, increased risks were found for cancers of the thyroid gland and other endocrine glands. For women, increased risks were found for cancers of the breast, endometrium, other female genitals (ovaries not included), stomach, colon, liver, pancreas, urinary bladder, skin, leukemia, and unspecified primary tumor. Unlike men, for women, no increased risk was found for cancer of the thyroid gland. In conclusions, levothyroxine treatment was associated with an excess cancer risk, including many different types of cancer, especially among women. Our results need confirmation by other studies, but levothyroxine is recommended to be prescribed only on approved indications.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
Cancer, Epidemiology, Gender, Levothyroxine
in
Cancer Epidemiology
volume
66
article number
101707
publisher
Elsevier
external identifiers
  • pmid:32222650
  • scopus:85082192246
ISSN
1877-7821
DOI
10.1016/j.canep.2020.101707
language
English
LU publication?
yes
id
ea2dfea2-cdb9-4bc0-a66d-a73d42ef1e5a
date added to LUP
2020-04-02 13:43:55
date last changed
2021-06-23 04:45:14
@article{ea2dfea2-cdb9-4bc0-a66d-a73d42ef1e5a,
  abstract     = {<p>High thyroid hormone values have been associated with an increased risk of incident cancers, especially breast cancer but also lung cancer and any solid cancers. We explored whether there is an increased risk of overall and cause-specific cancers in those receiving levothyroxine treatment. We included all individuals ≥ 18 years in Sweden (N = 8,573,313) on January 1 2009, and identified patients with two or more dispensed prescriptions of levothyroxine 2005–2006 (n = 253,193, 3.0 %). A cancer diagnosis in the Swedish Cancer Register 2009–2015 was used as outcome. We excluded patients with a cancer diagnosis before 2005. Cox regression was used (hazard ratios, HRs, and 95 % confidence intervals, CI) with adjustments for age, socioeconomic/neighborhood factors and co-morbidities. Totally 399,751 cases of incident cancer were identified, with a slight increased overall risk associated with levothyroxine treatment for both men, adjusted HR 1.06 (95 % CI 1.03–1.10), and women, adjusted HR 1.08 (95 % CI 1.07–1.10). For men, increased risks were found for cancers of the thyroid gland and other endocrine glands. For women, increased risks were found for cancers of the breast, endometrium, other female genitals (ovaries not included), stomach, colon, liver, pancreas, urinary bladder, skin, leukemia, and unspecified primary tumor. Unlike men, for women, no increased risk was found for cancer of the thyroid gland. In conclusions, levothyroxine treatment was associated with an excess cancer risk, including many different types of cancer, especially among women. Our results need confirmation by other studies, but levothyroxine is recommended to be prescribed only on approved indications.</p>},
  author       = {Wändell, Per and Carlsson, Axel C. and Li, Xinjun and Sundquist, Jan and Sundquist, Kristina},
  issn         = {1877-7821},
  language     = {eng},
  publisher    = {Elsevier},
  series       = {Cancer Epidemiology},
  title        = {Levothyroxine treatment is associated with an increased relative risk of overall and organ specific incident cancers – a cohort study of the Swedish population},
  url          = {http://dx.doi.org/10.1016/j.canep.2020.101707},
  doi          = {10.1016/j.canep.2020.101707},
  volume       = {66},
  year         = {2020},
}