Melatonin concentration before and during testosterone replacement in primary hypogonadic men.
OBJECTIVE
To study circadian levels of melatonin in primary hypogonadic adult men before and after testosterone treatment.


METHODS
Circadian serum melatonin profiles were studied in six men with primary hypogonadism before and during testosterone substitution and compared with an age-matched control group (n = 6).


RESULTS
Hypogonadal patients had higher plasma melatonin concentrations than the control group during day time (34.2 +/- 8.8 compared with 5.4 +/- 0.5 ng/l, means +/- SD; P < 0.005) and night-time (74.8 +/- 34.5 compared with 30.8 +/- 3.2 ng/l). A 3 months course of testosterone replacement treatment in the hypogonadal group was followed by a diminution of the amplified melatonin circadian rhythm, with lower mean values both during the day (34.2.8 +/- 8 compared with 12.7 +/- 2.45 ng/l, P < 0.001) and at night (74.8 +/- 34.5 compared with 41.5 +/- 13.5 ng/l, P < 0.01), and a decrease in the total area under the curve (958 +/- 318 compared with 475.5 +/- 222.9, P = 0.046). There was a significant negative correlation between melatonin (r = -0.69) and testosterone concentrations.


CONCLUSIONS
These data indicate that diminished testosterone in male primary hypogonadism is associated with enhanced plasma levels of melatonin, and that testosterone substitution treatment induces a deamplification of the circadian rhythm of melatonin values in humans.
Rajmil
O
O
Servei d'Andrologia, Fundació Puigvert, Barcelona, Spain.
Puig-Domingo
M
M
Tortosa
F
F
Viader
M
M
García Patterson
A
A
Schwarzstein
D
D
de Leiva
A
A
D000328:Adult; D002940:Circadian Rhythm; D006801:Humans; D007006:Hypogonadism / Q000097:blood* / Q000188:drug therapy*; D008297:Male; D008550:Melatonin / Q000097:blood*; D012016:Reference Values; D013739:Testosterone / Q000627:therapeutic use*
D013739:Testosterone; D008550:Melatonin