Spontaneous diurnal thyrotropin secretion is enhanced in proportion to circulating leptin in obese premenopausal women.
BACKGROUND
Recent evidence implicates leptin as an important modulator of thyroid axis activity.


OBJECTIVE
The objective of this study was to study spontaneous 24-h TSH secretion and 24-h circulating leptin concentrations in obese and lean women.


METHODS
This was a prospective parallel study (2004).


METHODS
This study was conducted at the Clinical Research Center (Leiden University Medical Center, Leiden, The Netherlands).


METHODS
Twelve healthy obese premenopausal women (body mass index, 33.2 +/- 0.9 kg/m2) and 11 lean controls (body mass index, 21.4 +/- 0.5 kg/m2) were studied in the follicular phase of their menstrual cycle.


METHODS
There were no interventions in this study.


METHODS
Spontaneous 24-h TSH concentrations (10-min time intervals) and secretion were calculated using waveform-independent deconvolution technique (pulse). Twenty-four-hour circulating leptin concentrations (20-min time intervals) were measured.


RESULTS
Mean TSH concentration (obese, 1.9 +/- 0.2 vs. lean, 1.1 +/- 0.1 mU/liter; P = 0.009) and secretion rate (obese, 43.4 +/- 5.5 vs. lean, 26.1 +/- 2.2 mU/liter distribution volume.24 h; P = 0.011) were substantially enhanced in obesity, whereas the fasting free T4 (fT4) concentrations were similar (fT4 in obese, 15.4 +/- 1.5 vs. in lean, 16.4 +/- 1.5 pmol/liter; P = 0.147). TSH secretion was positively related to 24-h leptin concentrations (r2= 0.31; P = 0.007).


CONCLUSIONS
TSH release is enhanced in the face of normal plasma fT4 concentrations in obese premenopausal women, and hyperleptinemia may well be involved in this neuroendocrine alteration.
Kok
Petra
P
Leiden University Medical Center, Department of General Internal Medicine (C4-83), P.O. Box 9600, 2300 RC Leiden, The Netherlands.
Roelfsema
Ferdinand
F
Frölich
Marijke
M
Meinders
A Edo
AE
Pijl
Hanno
H
D000328:Adult; D001823:Body Composition; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood*; D009765:Obesity / Q000378:metabolism*; D017697:Premenopause / Q000378:metabolism*; D011446:Prospective Studies; D017448:Receptors, Dopamine D2 / Q000502:physiology; D054411:Receptors, Leptin; D013972:Thyrotropin / Q000378:metabolism*
C515448:LEPR protein, human; D020738:Leptin; D017448:Receptors, Dopamine D2; D054411:Receptors, Leptin; D013972:Thyrotropin