Dissociation of leptin and body weight in hyperthyroid patients after radioiodine treatment.
OBJECTIVE
Leptin regulates energy production rates and body weight, which are frequently altered in hyperthyroidism. Data on a possible interaction between leptin and thyroid hormones are controversial. We assessed leptin serum concentrations, BMI, proportional fat tissue mass and thyroid hormones in hyperthyroid patients in a long-term follow-up after radioiodine therapy.


METHODS
The study included 28 hyperthyroid patients (mean age 66 y) before and up to one y after radioiodine therapy. Leptin and thyroid hormones, general parameters, BMI, proportional fat tissue (PFT) measurements by DEXA and thyroid morphology were recorded. Twenty-four age-matched euthyroid individuals (mean age 63 y) served as controls.


RESULTS
At baseline, leptin concentrations were significantly decreased in all hyperthyroid patients as compared to controls. One year after radioiodine therapy, 71% of the patients were euthyroid (group A) and 29% remained hyperthyroid (group B). BMI and PFT increased in both groups. While leptin concentrations remained low in group B, they normalised in group A after 6 to 12 months. Changes in leptin and thyroid hormone concentrations were positively correlated in group A patients (r=0.49, P=0.03) but not in patients remaining hyperthyroid.


CONCLUSIONS
Our data indicate a dissociation in the regulation of plasma leptin and BMI as well as proportional fat tissue in hyperthyroid patients which may be attributable to differences in lean and adipose mass weight gain after radioiodine therapy or direct influences of thyroid hormones on leptin regulation. International Journal of Obesity (2001) 25, 115-120
Division of Endocrinology and Nuclear Medicine, Department of Internal Medicine, Karl-Franzens University, Graz, Austria. barbara.obermayer@kfunigraz.ac.at
B M
BM
Obermayer-Pietsch
G E
GE
Frühauf
R W
RW
Lipp
G
G
Sendlhofer
T R
TR
Pieber
D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D015519:Bone Density; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000503:physiopathology / Q000532:radiotherapy*; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood
D007457:Iodine Radioisotopes; D020738:Leptin; D013963:Thyroid Hormones; D013972:Thyrotropin