Higher thyrotropin concentration is associated with increased incidence of colorectal cancer in older men.
BACKGROUND
Thyroid hormones regulate cellular survival and metabolism; however, their association with cancer incidence and death has not been well explored.


OBJECTIVE
Our aim was to examine the relationship between thyrotropin (TSH) and free thyroxine (FT4) with cancer incidence (all cancers, prostate, colorectal and lung cancer). Associations with cancer-related deaths were also explored.


METHODS
A prospective cohort study involving community-dwelling men aged 70-89 years.


METHODS
Thyroid hormones were measured in 3836 men between 2001 and 2004. Competing risks analyses were used to perform longitudinal analyses with results expressed as subhazard ratios (SHR). Outcomes were ascertained through electronic linkage until 20 June 2013.


RESULTS
Mean age was 77·0 ± 3·6 years. A total of 864 men developed cancers, and 506 experienced cancer-related deaths. A total of 340, 136 and 119 men developed prostate, colorectal and lung cancers, respectively. After adjustments, there were no associations between TSH and incidence of all cancers, prostate or lung cancer. Higher TSH was associated with increased colorectal cancer incidence (SHR = 1·19, 95% CI 1·00-1·42; P = 0·048 for every 1 SD increase in log TSH). This association was strengthened after excluding the first year of follow-up (SHR = 1·23, 95% CI 1·02-1·48, P = 0·028). FT4 was not associated with incidence of all cancers, prostate, colorectal or lung cancer. Thyroid hormones were not associated with cancer-related deaths.


CONCLUSIONS
In community-dwelling older men, FT4 was not associated with cancer incidence. Higher TSH is independently associated with increased incidence of colorectal cancer. Further investigation is warranted to determine whether a causal relationship exists.
School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia.|Department of Endocrinology and Diabetes, Fiona Stanley Hospital, Perth, WA, Australia.
Yi X
YX
Chan
Department of Epidemiology and Biostatistics, School of Public Health, Curtin University, Perth, WA, Australia.
Helman
H
Alfonso
School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia.|Pathwest Laboratory Medicine, Fiona Stanley Hospital, Perth, WA, Australia.
Stephen Anthony Paul
SA
Chubb
Department of Endocrinology and Diabetes, Fiona Stanley Hospital, Perth, WA, Australia.
Peter Gerard
PG
Fegan
School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia.|Department of Neurology, Sir Charles Gairdner Hospital, Perth, WA, Australia.
Graeme J
GJ
Hankey
Queensland Research Centre for Peripheral Vascular Disease, College of Medicine and Dentistry, James Cook University, Townsville, Qld, Australia.|Department of Vascular and Endovascular Surgery, The Townsville Hospital, Townsville, Qld, Australia.
Jonathan
J
Golledge
School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia.|Western Australian Centre for Health and Ageing, Centre for Medical Research, University of Western Australia, Perth, WA, Australia.
Leon
L
Flicker
School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia.|Department of Endocrinology and Diabetes, Fiona Stanley Hospital, Perth, WA, Australia.
Bu B
BB
Yeap
D000367:Age Factors; D000368:Aged; D015179:Colorectal Neoplasms / Q000097:blood* / Q000401:mortality; D005260:Female; D006801:Humans; D015994:Incidence; D008175:Lung Neoplasms / Q000097:blood / Q000401:mortality; D008297:Male; D009369:Neoplasms / Q000097:blood / Q000401:mortality; D011471:Prostatic Neoplasms / Q000097:blood / Q000401:mortality; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood
D013972:Thyrotropin; D013974:Thyroxine