High circulating thyrotropin levels in obese women are reduced after body weight loss induced by caloric restriction.
BACKGROUND
Previous clinical studies concerning the impact of body weight loss on single plasma TSH concentration measurements or the TSH response to TRH in obese humans have shown variable results.


OBJECTIVE
The objective of this study was to investigate the effect of weight loss induced by caloric restriction on diurnal TSH concentrations and secretion in obese humans.


METHODS
This was a clinical, prospective, crossover study.


METHODS
The study was conducted at the Clinical Research Center of Leiden University Medical Center.


METHODS
Eleven obese premenopausal women (body mass index, 33.3 +/- 0.7 kg/m2) were studied.


METHODS
The study intervention was weight loss (50% reduction overweight by caloric restriction).


METHODS
Twenty-four-hour plasma TSH concentrations (10-min intervals) and the 24-h TSH secretion rate, calculated by a waveform-independent deconvolution technique (Pulse), were determined.


RESULTS
The 24-h TSH secretion rate was significantly higher in obese women than in normal weight controls, and weight loss was accompanied by diminished TSH release (before weight loss, 43.4 +/- 6.4 mU/liter.24 h; after weight loss, 34.4 +/- 5.9 mU/liter.24 h; P = 0.02). Circulating free T3 levels decreased after weight loss from 4.3 +/- 0.19 to 3.8 +/- 0.14 pmol/liter (P = 0.04). Differences in 24-h TSH release correlated positively with the decline of circulating leptin (r2 = 0.62; P < 0.01).


CONCLUSIONS
Elevated TSH secretion in obese women is significantly reduced by diet-induced weight loss. Among various physiological cues, leptin may be involved in this phenomenon. The decreases in TSH and free T3 may blunt energy expenditure in response to long-term calorie restriction, thereby frustrating weight loss attempts of obese individuals.
Kok
Petra
P
Department of General Internal Medicine (C4-83), Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
Roelfsema
Ferdinand
F
Langendonk
Janneke G
JG
Frölich
Marijke
M
Burggraaf
Jacobus
J
Meinders
A Edo
AE
Pijl
Hanno
H
D000328:Adult; D031204:Caloric Restriction; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D004038:Diet, Reducing; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood; D009765:Obesity / Q000097:blood* / Q000178:diet therapy*; D011446:Prospective Studies; D013972:Thyrotropin / Q000097:blood*; D015431:Weight Loss
D020738:Leptin; D013972:Thyrotropin