Phil B.FontanarosaMD, Deputy EditorIndividualAuthorStephen J.LurieMD, PhD, Fishbein FellowIndividualAuthor
To the Editor: Dr Heymsfield and colleagues1 documented the effect of exogenous leptin administration
on body weight and showed that only patients in the highest dose groups had
significant weight loss compared with those taking placebo. We suggest that
the physiological characteristics of leptin may be relevant to its pharmacokinetics.
Diurnal and ultradian oscillations are essential characteristics of
hormone secretion. Leptin is characterized by nyctohemeral rhythms, with serum
leptin concentrations being highest around midnight.2
This pattern closely resembles the circadian rhythmicity of other hormones,
such as thyrotropin and prolactin, and precedes the peak concentrations of
cortisol and growth hormone. To what extent the nocturnal increase in leptin
is related to biological activity remains to be clarified. In humans, the
nocturnal increase in leptin secretion seems to be entrained to meal timing
and most likely is related to the cumulative hyperinsulinemia from food ingestion
during the entire waking period.
Frühbeck G, Díez-Caballero A, Salvador J, Alvarez-Cienfuegos J. Chronobiology of Recombinant Leptin Therapy. JAMA. 2000;283(12):1567-1568. doi:10.1001/jama.283.12.1563