Abstract
The aim of the study was to investigate the influence of hyperthyroidism and/or hypothyroidism on adrenergic regulation of lipolysis in situ using the microdialysis method. The disturbances of thyroid hormone levels were shown to modify the adrenergic regulation of lipolysis in vitro but no study has examined the effect in vivo resp. in situ. 8 hyperthyroid and 14 hypothyroid patients were examined on two occasions: first, just after the diagnosis of thyroid disease was established and, then after treatment, when patients became euthyroid.
On each occasion, the abdominal subcutaneous adipose tissue was perfused with two graded concentrations (0.1 a 1 microml/l) of isoproterenol and the response of interstitial glycerol concentration (IGC), as an index of lipolysis, was observed in the dialysate outflowing from the microdialysis probe. In addition, the blood flow in the adipose tissue was estimated using ethanol washout method Before the treatment, the increase of IGC was higher in hyperthyroid patients compared with hypothyroid ones (area-under-curve (AUC): 11222.1 +- 3544 micromol/l/30min vs. 2478.4 +- 1110 micromol/l/30min, P < 0.05) whereas, after treatment, the responses of ICG were not different between the two groups (5044.4 +- 980 micromol/l/30min vs. 5402.1 +- 1150 micromol/l/30min, NS).
The response of adipose tissue blood flow to isoproterenol stimulation tended to be higher in hyperthyroid patients. The results suggest that the modulatory effect of thyroid hormones on beta-adrenergic stimulation of lipolysis in adipose tissue is functional in vivo in patiens with thyroid dysfunction.