Thyreotropin levels in diabetic patients on metformin treatment.
OBJECTIVE
A retrospective study to evaluate the changes in TSH concentrations in diabetic patients treated or not treated with metformin and/or L-thyroxine (L-T(4)).


METHODS
Three hundred and ninety three euthyroid diabetic patients were divided into three groups on the basis of metformin and/or L-T(4) treatment: Group (M-/L-), 119 subjects never treated with metformin and L-T(4); Group (M+/L-), 203 subjects who started metformin treatment at recruitment; and Group (M+/L+), 71 patients on L-T(4) who started metformin recruitment.


RESULTS
The effect of metformin on serum TSH concentrations was analyzed in relation to the basal value of TSH (below 2.5 mIU/L (Q1) or between 2.51 and 4.5 mIU/L (Q2)). In patients of group M+/L+, TSH significantly decreased independently from the basal level (Q1, from 1.450.53 to 1.011.12 mU/L (P=0.037); Q2, from 3.600.53 to 1.910.89 mU/L (P<0.0001)). In M+/L group, the decrease in TSH was significant only in those patients with a basal high-normal serum TSH (Q2: from 3.24±0.51 to 2.27±1.28 mU/l (P=0.004)); in M-/L- patients, no significant changes in TSH levels were observed. In patients of group M+/L showing high-normal basal TSH levels, a significant decrease in TSH was observed independently from the presence or absence of thyroid peroxidase antibodies (ABTPO; Q2 ABTPO +: from 3.38±0.48 to 1.87±1.08 mU/l (P<0.001); Q2 AbTPO -: from 3.21±0.52 to 2.34±1.31 mU/l (P<0.001)).


CONCLUSIONS
These data strengthen the known TSH-lowering effect of metformin in diabetic patients on L-T(4) treatment and shows a significant reduction of TSH also in euthyroid patients with higher baseline TSH levels independently from the presence of AbTPO.
Endocrine and Metabolic Unit, Department of Medical and Surgical Sciences, Clinica Medica, University of Brescia, c/o 1 Medicina Spedali Civili Piazzale Spedali Civili 1, 25100 Brescia, Italy. cappelli@med.unibs.it
Carlo
C
Cappelli
Mario
M
Rotondi
Ilenia
I
Pirola
Barbara
B
Agosti
Annamaria
A
Formenti
Emanuela
E
Zarra
Umberto
U
Valentini
Paola
P
Leporati
Luca
L
Chiovato
Maurizio
M
Castellano
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood; D048909:Diabetes Complications / Q000097:blood / Q000188:drug therapy; D003920:Diabetes Mellitus / Q000097:blood* / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D007037:Hypothyroidism / Q000097:blood / Q000150:complications / Q000188:drug therapy; D008297:Male; D008687:Metformin / Q000008:administration & dosage / Q000627:therapeutic use*; D008875:Middle Aged; D019338:Polypharmacy; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D001323:Autoantibodies; D007004:Hypoglycemic Agents; C056626:thyroid microsomal antibodies; D014284:Triiodothyronine; D013972:Thyrotropin; D008687:Metformin; D013974:Thyroxine