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Bromocriptine Reduces Augmented Thyrotropin Secretion in Obese Premenopausal Women

Departments of General Internal Medicine (P.K., A.E.M.), Endocrinology and Metabolic Diseases (F.R., H.P.), and Clinical Chemistry (M.F., J.v.P.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands

Address all correspondence and requests for reprints to: Ferdinand Roelfsema, Leiden University Medical Center, Department of Endocrinology and Metabolic Diseases, P.O. Box 9600, 2300 RC Leiden, The Netherlands. E-mail: f.roelfsema{at}lumc.nl.

Context: Diurnal TSH secretion is enhanced in obese premenopausal women. Dopamine inhibits TSH secretion through activation of dopamine D₂ receptors (D₂R). Dopamine D₂R availability in the brain is reduced in obese humans in proportion to body adiposity. We hypothesized that deficient dopamine D₂R signaling is involved in the enhanced TSH secretion associated with obesity.

Objective: The effect of short-term bromocriptine treatment on spontaneous TSH secretion in obese women was studied while body weight and caloric intake remained constant.

Design and Setting: We conducted a prospective, fixed-order, crossover study in a Clinical Research Center.

Participants: Seventeen obese women (body mass index, 33.2 ± 0.6 kg/m²) were studied twice in the early follicular phase of their menstrual cycle.

Intervention: Subjects were treated for 8 d with placebo and bromocriptine.

Main Outcome Measure(s): Blood was collected for 24 h at 10-min intervals, and TSH and leptin were analyzed with deconvolution and correlation techniques, approximate entropy, and cosine regression.

Results: Bromocriptine reduced 24-h TSH secretion (placebo, 29.8 ± 4.6 mU/liter · 24 h, vs. bromocriptine, 22.4 ± 3.7 mU/liter · 24 h; P = 0.001), whereas free T₄ and total T₃ concentrations did not change. Bromocriptine administration reduced the mesor and amplitude of the 24-h rhythm without resetting the phase. The regularity of the subordinate TSH pattern and synchrony between leptin and TSH were unaffected by bromocriptine.

Conclusion: Activation of dopamine D₂R by bromocriptine reverses enhanced diurnal TSH secretion in obese women. Thus, reduced dopaminergic neuronal signaling might be involved in the perturbation of the thyrotrope hormonal axis in obese premenopausal women.

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				F. Roelfsema, A. M. Pereira, J. D. Veldhuis, R. Adriaanse, E. Endert, E. Fliers, and J. A. Romijn Thyrotropin Secretion Profiles Are Not Different in Men and Women J. Clin. Endocrinol. Metab., October 1, 2009; 94(10): 3964 - 3967. [Abstract] [Full Text] [PDF]