The DOI matches its Crossref record; 31 of the 32 references it cites were found in a registry or an index, and 1 are not checked yet; none of the 14 sources its claims cite is checked for support yet.
Endogenous testosterone levels and smoking in men. The fifth Tromsø study
Open accessAbstract
Summary: Smoking is a risk factor of coronary heart disease (CHD), while the role of testosterone in the development of CHD is controversial. The reported effects of cigarette smoking on testosterone levels in men are conflicting, and smoking may be an important confounding factor when evaluating the relationship between testosterone levels and CHD. Thus, the objective of the present study was to examine the associations of smoking status and number of cigarettes smoked per day with total and free testosterone levels in a cross‐sectional population‐based study of 3427 men participating in the fifth Tromsø study. Total testosterone, luteinizing hormone, follicle‐stimulating hormone and sex hormone‐binding globulin levels were measured with immunoassay while free testosterone levels were calculated. Waist circumference was also measured and two standardized questionnaires were completed, including smoking status and number of cigarettes smoked. The data were analysed with analysis of variance and covariance and multiple regression analysis. Smoking men had significantly higher levels of total and free testosterone compared with men who never smoked (p < 0.001 and <0.01 respectively). Both total and free testosterone levels increased significantly with increasing number of cigarettes smoked daily (p < 0.001). Smoking men had 15% higher total and 13% higher free testosterone levels compared with men who never smoked. Thus, smoking seems to be an important confounding factor when evaluating testosterone levels, and could possibly mask borderline hypogonadism.
Checked 2026-11-05 · 1 reference not checked yet
Overview
AI snapshot
Written from the paper’s full text.
TL;DR
In the fifth Tromsø study, smoking men had significantly higher total and free testosterone levels than never-smokers, and levels rose with the number of cigarettes smoked daily. The authors conclude smoking is an important confounding factor when evaluating testosterone levels and could mask borderline hypogonadism.
Key findings
- Smokers had higher total testosterone than never-smokers (15.5 vs. 13.6 nmol/L, p < 0.001) and higher free testosterone (285 vs. 269 pmol/L, p < 0.01).
- Smoking men had 15% higher total and 13% higher free testosterone levels compared with men who never smoked.
- Total and free testosterone increased significantly with increasing number of cigarettes smoked daily, both before and after adjustment for age and waist circumference (p < 0.001).
- Previous smokers had total testosterone almost identical to never-smokers (13.5 vs. 13.6 nmol/L); smoking was also an independent positive predictor of SHBG (p < 0.001).
Methods
- Cross-sectional, population-based study of 3427 men from the fifth Tromsø study (2001); total testosterone was measured in 3447 men, and smoking status was recorded in 3427.
- Total testosterone, LH, FSH, and SHBG were measured by immunoassay; free testosterone was calculated from total testosterone and SHBG using a fixed albumin value. Waist circumference and self-administered questionnaires on smoking, physical activity, and alcohol were used.
- Analyses included Student’s t-test, analysis of variance/covariance, and multiple linear regression, with two-tailed p < 0.05 considered significant.
Limitations
- The paper states hormone levels were based on a single sample drawn between 08.30 and 18.30 h, not preferably in the morning due to diurnal variation; adjusting for sampling time did not change associations.
- The paper states free testosterone was calculated, not measured, though the calculation was reported as reliable; smoking status and number of cigarettes were self-reported, so misclassification cannot be excluded.
- The paper states the most important limitation is the cross-sectional design, so the direction of associations cannot be determined.
Model-written summary. Check it against the paper before relying on it.
Integrity signals
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Statistics
Verification
Claims the paper makes
0 of 14 cited sources checked · 0 supported · 0 flagged
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Total and free testosterone levels were higher in smokers compared with men who never smoked (15.5 nmol/L vs. 13.6 nmol/L, p < 0.001; and 285 pmol/L vs. 269 pmol/L, p < 0.01; respectively).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIn the paper
“Table 3 also shows that smoking was positively and independently associated with SHBG, after adjusting for free testosterone.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
What the sources say
- Not matchedcites Table 3
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passes- Not matched
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Total and free testosterone levels were higher in smokers compared with men who never smoked (15.5 nmol/L vs. 13.6 nmol/L, p < 0.001; and 285 pmol/L vs. 269 pmol/L, p < 0.01; respectively).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Total and free testosterone was positively associated with the number of cigarettes smoked, both before and after adjustment for age and WC (p < 0.001 and <0.001 respectively).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Smokers had slightly higher LH levels (5.7 IU/L vs. 5.3 IU/L, p < 0.05) compared with never smokers”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIn the paper
“Smoking was a positive and independent predictor of both total and free testosterone levels in multiple linear regression analyses (Table 3).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
What the sources say
- Not matchedcites Table 3
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Not matched
In the paper
“Table 4 also shows that SHBG was positively associated with number of cigarettes smoked after adjusting for age and WC (P < 0.001).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
What the sources say
- Not matchedcites Table 4
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passes- Not matched
In the paper
“Smoking was a positive and independent predictor of both total and free testosterone levels in multiple linear regression analyses (Table 3).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
What the sources say
- Not matchedcites Table 3
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Not matched
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In previous smokers the level of total testosterone was almost identical to that observed in those who had never smoked (13.5 nmol/L vs. 13.6 nmol/L).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Smoking was not an independent predictor of LH and FSH (data not shown).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passes
- It may state two separate claims as one. 12
- Probably not a substantial claim. 8
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Smoking duration was not associated with hormone levels or SHBG levels (data not shown).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Smoking men had 15% higher total and 13% higher free testosterone levels compared with men who never smoked.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“We did not measure free testosterone but used calculated values.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Hormone levels were based on a single sample, drawn between 08.30 and 18.30 h.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Total testosterone was measured in 3447 men, and among them, smoking status was recorded in 3427.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Strength:plain· not yet calibratedn = 3,447Tests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The most important limitation, of course, is that the results are cross-sectional, and the direction of the associations cannot be determined.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If this were true, testosterone levels would be expected to remain elevated in men who stopped smoking, but they were not.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“Thus, men with higher testosterone levels are reportedly more often engaged in health risk behaviour than men with low levels, and are more likely to smoke than controls (Booth et al., 1999).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
What the sources say
- Not checked — no full text of the sourcecites Booth et al., 1999 source
Strength:hedged· not yet calibratedCausal:correlational· not yet calibratedTests✗ Asserted: fails✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The authors may not put it forward as true. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This is by far the largest population-based study investigating the association between smoking status and total and free testosterone levels.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Discussion
Strength:boosted· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“However, adjusting for SHBG in our study did not change the association between total and free testosterone and smoking, nor did adjusting for free testosterone change the association between SHBG and smoking.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, smoking seems to be an important confounding factor when evaluating testosterone levels, and could possibly mask borderline hypogonadism.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“A total of 10 353 men and women were invited to participate, and 8130 (3511 men) attended the study.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Results
Strength:plain· not yet calibratedn = 3,511Tests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Smoking status and the number of cigarettes smoked were self-reported, and we cannot exclude some misclassification.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“The results are supported by two large cross-sectional studies, our own previous smaller study (Svartberg et al., 2003) and the study by Field et al. (1994).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Discussion
What the sources say
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Finally, although smoking men had 15% higher total and 13% higher free testosterone levels, it is not likely that the observed differences in testosterone levels would affect sexual behaviour or clinical symptoms.”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✗ Based: failsProbably not a substantial claim. The paper may give no reason why it holds.
In the paper
“The results were similar, with higher levels of total and free testosterone in each subgroup (Fig. 1).”
§ Endogenous testosterone levels and smoking in men. The fifth Tromsø study > Barrett
What the sources say
- Not matchedcites Fig. 1
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
- Not matched
The paper relies on this without support.
Smoking may be an important confounding factor when evaluating the relationship between testosterone levels and CHD.
“As smoking may be an important confounding factor when evaluating the relationship between testosterone levels and CHD, it is important to better understand the associations between smoking and testosterone levels.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The cited source doesn’t support the claim as written.
In the citing paper
“Previous studies of cigarette smoking, alcohol consumption and physical activity with sex steroid hormones and SHBG levels in men were limited by small sample sizes [22], were restricted to older men [17], or both [20].”
From Association of cigarette smoking, alcohol consumption, and physical activity with sex steroid hormone levels in US men (2009) · cites this paper as [20]
Checked by a reasoning model — may be wrong.
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“the majority of studies which also included SHBG levels confirmed that SHGB levels in smokers are higher, and both free and total testosterone are increased in smokers”
From Effects of Smoking Cessation on Hormonal Levels in Men (2013) · cites this paper as Svartberg and Jorde 2007
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“In some studies, current smokers had higher circulating concentrations of total testosterone, free testosterone, total estradiol and sex hormone-binding globulin (SHBG) [16, 18–23]”
From Association of cigarette smoking, alcohol consumption, and physical activity with sex steroid hormone levels in US men (2009) · cites this paper as [20]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Adiposity is a well-known modifiable predictor of sex steroid hormones in men [14, 16–20]”
From Association of cigarette smoking, alcohol consumption, and physical activity with sex steroid hormone levels in US men (2009) · cites this paper as [20]
Experimental — accuracy not yet measuredThe cited source says what the claim attributes to it.
In the citing paper
“Further, in agreement with previous studies, 14,31 adjustment for SHBG in our study did not change the association between testosterone levels and smoking.”
From Cigarette smoking has a positive and independent effect on testosterone levels (2013) · cites this paper as [31]
Citations
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Flagged first, then by citations
Research works printed but not linked: 1
- Critchley J., 2004, Smoking cessation for the secondary prevention of coronary hearth disease, Cochrane Database of Systematic Reviews, 1, CD003041
Cited by
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Metadata
- Authors
- Svartberg, J., & Jorde, R.
- Affiliations
- University Hospital of North Norway (NO)
- Corresponding author
- Svartberg, Johan
- ORCID
- Jorde, Rolf
- Venue
- International Journal of Andrology
- Publisher
- Wiley
- Published
- 2006-11-29
- Volume
- 30
- Issue
- 3
- Pages
- 137-143
- ISSN
- 0105-6263 (ISSN-L)
- 1365-2605
- OpenAlex
- W1999593787
- Cited by
- 111
- References
- 27
- Citations by year
- 2026: 5 · 2025: 2 · 2024: 12 · 2023: 6 · 2022: 8 · 2021: 11 · 2020: 2 · 2019: 3 · 2018: 4 · 2017: 4 · 2016: 7 · 2015: 10 · 2014: 5 · 2013: 2 · 2012: 5
- FWCI
- 2.57
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- International Journal of Andrology (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Hormonal and reproductive studies
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Smoking Behavior and Cessation
- Health Sciences › Medicine › Reproductive Medicine › Sperm and Testicular Function
- Keywords
- testosterone, smoking, free testosterone, total testosterone, cigarette smoking, coronary artery disease, confounding factor, hypogonadism, luteinizing hormone, follicle-stimulating hormone, sex hormone-binding globulin, men, waist circumference
- MeSH terms
- Adult, Aged, Analysis of Variance, Cross-Sectional Studies, Female, Humans, Male, Middle Aged, Surveys and Questionnaires, Regression Analysis, Sex Factors, Smoking, Testosterone
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