Amplification of nocturnal melatonin secretion in women with functional hypothalamic amenorrhea

Plasma melatonin levels were determined by a sensitive RIA at 30 min intervals for 24h in 7 women with functional hypothalamic amenorrhea (HA) and in 7 age and season matched normal cycling women in the early follicular phase (NC). While daytime melatonin concentrations were nondetectable in both groups, the integrated nocturnal levels were 3-fold greater in HA (244 ± 58 (se) vs 74 ± 32 pmol-min/L×10³, p<0.005). This melatonin increase in HA was due to an elevated peak amplitude (p<0.01) and extended duration (p<0.05). The latter was mostly due to a significant delay in the offset time of the amplified nocturnal melatonin secretion.