Skip Navigation

This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF ) Freely available
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Search for citing articles in:
ISI Web of Science (6)
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Hjollund, N. H. I.
Right arrow Articles by Olsen, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hjollund, N. H. I.
Right arrow Articles by Olsen, J.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Human Reproduction, Vol. 17, No. 7, 1837-1838, July 2002
© 2002 European Society of Human Reproduction and Embryology

Correlation of scrotal temperature in twins: Brief Communication

Niels Henrik I. Hjollund1,5, Lone Storgaard1, Erik Ernst2, Jens Peter E. Bonde1, Kaare Christensen3 and Jørn Olsen4

1 Department of Occupational Medicine, Aarhus University Hospital, 2 Reproductive Toxicology Unit, Institute of Neurobiology, Aarhus University, 3 Epidemiology Institute of Public Health, University of Southern Denmark and 4 Danish Epidemiology Science Centre, Aarhus University, Denmark


   Abstract
Top
 Abstract
Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
BACKGROUND: Scrotal temperature and semen quality have been found to be inversely correlated in several studies, and variation in scrotal temperature may contribute to the well known variation in semen quality. The reason for the variation in scrotal temperature is not well understood although determinants could be of a genetic nature. METHODS: We monitored scrotal skin temperature for 24 h in a group of monozygotic and dizygotic twins and single-born brothers (n = 48 males). A thermistor was attached to the underwear and the temperature of the scrotal skin was recorded every 5 min using a small portable data logger. RESULTS: A correlation in median scrotal temperature was found among monozygotic twins (r = 0.64, P = 0.01), but not in dizygotic twins and single-born brothers (r = 0.17, NS). Similar results were found for other percentiles of temperature. CONCLUSIONS: The results suggest a genetic component to the variation in scrotal temperature. An hereditary element in male fecundity may be expressed through scrotal temperature, which constitutes a mechanism independent of those responsible for the development of the sperm producing epithelium.

Key words: heredity/semen quality/temperature/twins/varicocele


   Introduction
Top
 Abstract
 Introduction
Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
The biological background for the large inter-individual differences in sperm count is unknown, although differences in the temperature of the male gonads have been proposed as a possible determinant (Bedford, 1991Go; Spira, 1991Go; Mieusset and Bujan, 1995Go; Setchell, 1998Go). Several studies in human populations have found a higher scrotal temperature in infertile men compared with fertile controls, regardless of the cause of impaired fertility, e.g. varicocele (Mieusset et al., 1987Go; Zorgniotti and Sealfon, 1988Go; Mieusset, 1991Go). Likewise in population based samples a negative association between scrotal temperature and sperm concentration has been demonstrated (Hjollund et al., 2000Go). The reason for the variation in scrotal temperature is not well understood although determinants could be of genetic nature. The aim of this communication is to report how scrotal temperature correlates in monozygotic twins.


   Materials and methods
Top
 Abstract
 Introduction
 Materials and methods
Results
 Discussion
 Acknowledgements
 References
 
Our participants originated from a larger study of semen quality in twins and single-born brothers (Storgaard et al., 2002Go). All men enrolled from January 19 to April 13, 2000 were asked to participate in this supplementary programme with temperature measurement. Scrotal skin temperature was measured continuously for 24 h on a day selected by the participant as representative of a normal day. A thermistor was attached to the underwear and the temperature of the scrotal skin was recorded every 5 min with a small portable recording device (Tinytalk®, Gemini Data Loggers Ltd, UK) (Hjollund et al., 2000Go). A total of 101 men was monitored, and 48 men from complete pairs of brothers were available for analysis: monozygotic twins (15 pairs), dizygotic twins (six pairs) and single-born brothers (three pairs). Individual variability in scrotal temperature is considerable and we do not know if for example, occurrence of warm periods are more important than absence of cold periods. In both cases a similar increase in mean temperature would appear and consequently the scrotal temperature cannot be described by one statistic, such as the median or the mean, without a possible loss of important information. Accordingly, we calculated five summary measures of temperature for each participant: the 10th, the 25th, the 50th (median), the 75th and the 90th percentile. Intra-class correlation coefficients were calculated as 2 x co-varianceab/(variancea+ varianceb), where a and b are twin A/big brother and twin B/little brother respectively (Neale and Cardon, 1992Go).


   Results
Top
 Abstract
 Introduction
 Materials and methods
 Results
Discussion
 Acknowledgements
 References
 
A strong and consistent correlation was found among monozygotic twins for all summary measures of diurnal temperature (Table IGo). The correlations among monozygotic twins were consistently higher than among dizygotic twins and single-born brothers. The same pattern was found when night-time and day-time temperatures were analysed separately (data not shown). Analyses without the six single-born brothers provided essentially the same estimates, but with broader confidence intervals. A sedentary work position is a significant determinant of scrotal temperature (Bujan et al., 2000Go; Hjollund et al., 2000Go), but was only weakly correlated among monozygotic twins (r = 0.47, NS) and adjustment of temperature with respect to sedentary work position had little effect on the correlations in temperature.


View this table:
[in this window]
[in a new window]
  		Table I. Correlation in 24 h scrotal skin temperature in monozygotic twins compared to dizygotic twins and single-born brothers
 

   Discussion
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
Acknowledgements
 References
 
So far only one study has compared measures of semen quality in twins. In a group of 17 pairs of male twins, Handelsman found a high correlation in sperm concentration as well as sperm output (Handelsman, 1997Go). The study had insufficient power to distinguish between genetic factors and shared environment. We found evidence suggestive of a genetic contribution to the variation in scrotal temperature. Although the exact role of testicular temperature on spermatogenesis still remains to be settled, our results suggest that a hereditary element in male fecundity may be expressed through mechanisms other than those responsible for the development of the sperm-producing epithelium itself.


   Acknowledgements
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
References
 
The study was supported by the Danish Medical Research Council (Jnr 9802562). The Danish Ministry of Health: Research Centre for Environmental Health (Jnr 383–4–1999), and The Danish Health Insurance Fund (Jnr 11/207–98 and 2000B514). The activities of the Danish Epidemiology Science Centre are financed by a grant from the Danish National Research Foundation.


   Notes
 
5 To whom correspondence should be addressed at: Department of Occupational Medicine, Aarhus University Hospital, Noerrebrogade 44, DK-8000 Aarhus C, Denmark. E-mail: hhjol{at}akh.aaa.dk Back


   References
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
Bedford, J.M. (1991) Effects of elevated temperature on the epididymis and testis: experimental studies. Adv. Exp. Med. Biol., 286, 19–32.[Medline]

Bujan, L., Daudin, M., Charlet, J.P., Thonneau, P. and Mieusset, R. (2000) Increase in scrotal temperature in car drivers. Hum. Reprod., 15, 1355–1357.[Abstract/Free Full Text]

Handelsman, D.J. (1997) Estimating familial and genetic contributions to variability in human testicular function: a pilot twin study. Int. J. Androl., 20, 215–221.[ISI][Medline]

Hjollund, N.H., Bonde, J.P., Jensen, T.K., and Olsen, J. (2000) Diurnal scrotal skin temperature and semen quality. Int. J. Androl., 23, 309–318.[Medline]

Mieusset, R. (1991) Scrotal hyperthermia; etiologic factors: facts and hypotheses. Adv. Exp. Med. Biol., 286, 211–216.[Medline]

Mieusset, R. and Bujan, L. (1995) Testicular heating and its possible contributions to male infertility: a review. Int. J. Androl., 18, 169–184.[ISI][Medline]

Mieusset, R., Bujan, L., Mondinat, C., Mansat, A., Pontonnier, F. and Grandjean, H. (1987) Association of scrotal hyperthermia with impaired spermatogenesis in infertile men. Fertil. Steril., 48, 1006–1011.[Medline]

Neale, M.C. and Cardon, L.R. (1992) Methodology for genetic studies of twins and families. Kluwer Academic Publishers, Dordrecht, The Netherlands.

Setchell, B.P. (1998) The Parkes Lecture. Heat and the testis. J. Reprod. Fertil., 114, 179–194.[Abstract]

Spira, A. (1991) Epidemiologic aspects of the relationship between temperature and male reproduction. Adv. Exp. Med. Biol., 286, 49–56.[Medline]

Storgaard, L., Bonde, J.P., Ernst, E., Andersen, C.Y, Kyvik, K.O. and Olsen, J. (2002) Prenatal estrogen exposure and semen quality: a study on twins. Br. Med. J., (in press).

Zorgniotti, A.W. and Sealfon, A.I. (1988) Measurement of intrascrotal temperature in normal and subfertile men. J. Reprod. Fertil., 82, 563–566.[Abstract]

Submitted on November 26, 2001; accepted on March 11, 2002.


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 Hum ReprodHome page
A. Jung, F. Leonhardt, W.-B. Schill, and H.-C. Schuppe
Influence of the type of undertrousers and physical activity on scrotal temperature
Hum. Reprod., April 1, 2005; 20(4): 1022 - 1027.
[Abstract] [Full Text] [PDF]

Home page
 J AndrolHome page
J. G. Alvarez
Nurture vs Nature: How Can We Optimize Sperm Quality?
J Androl, September 1, 2003; 24(5): 640 - 648.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF ) Freely available
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Search for citing articles in:
ISI Web of Science (6)
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Hjollund, N. H. I.
Right arrow Articles by Olsen, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hjollund, N. H. I.
Right arrow Articles by Olsen, J.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?