Responsiveness of the reproductive axis to a single missed evening meal in young adult males.
OBJECTIVE
The male reproductive axis is responsive to energetic deficits, including multiday fasts, but little is known about brief periods of fasting (<24 hours). Reduced testosterone in low-energy balance situations is hypothesized to reflect redirection of resources from reproduction to survival. This study tests the hypothesis that testosterone levels decrease during a minor caloric deficiency by assessing the effects of a single missed (evening) meal on morning testosterone in 23 healthy male participants, age 19-36.


METHODS
Participants provided daily saliva and urine samples for two baseline days and the morning following an evening fast (water only after 4 PM). Testosterone, cortisol, and luteinizing hormone were measured with enzyme immunoassays.


RESULTS
Fasting specimens had significantly lower overnight urinary luteinizing hormone (P = 0.045) and morning salivary testosterone than baseline (P = 0.037). In contrast to morning salivary testosterone, there was a significant increase in overnight urinary testosterone (P = 0.000) following the evening fast, suggesting an increase in urinary clearance rates. There was a marginal increase in overnight urinary cortisol (P = 0.100), but not morning salivary cortisol (P = 0.589).


CONCLUSIONS
These results suggest the male reproductive axis may react more quickly to energetic imbalances than has been previously appreciated.
Trumble
Benjamin C
BC
Department of Anthropology, University of Washington, Seattle, Washington 98195, USA. btrumble@uw.edu
Brindle
Eleanor
E
Kupsik
Michalina
M
O'Connor
Kathleen A
KA
D000328:Adult; D004032:Diet; D005215:Fasting / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis* / Q000652:urine; D007124:Immunoenzyme Techniques; D007986:Luteinizing Hormone / Q000652:urine*; D008297:Male; D012463:Saliva / Q000737:chemistry*; D013739:Testosterone / Q000032:analysis* / Q000652:urine
D013739:Testosterone; D007986:Luteinizing Hormone; D006854:Hydrocortisone