The effect of metformin on the hypothalamic-pituitary-thyroid axis in patients with type 2 diabetes and amiodarone-induced hypothyroidism.
BACKGROUND
Chronic metformin treatment was found to reduce elevated thyrotropin levels. Amiodarone treatment is associated with a range of effects in thyroid function from mild derangements to overt thyroid dysfunction. No previous study has investigated the effect of metformin on hypothalamic-pituitary-thyroid axis activity in patients with amiodarone-induced hypothyroidism.


METHODS
The study included three age-, sex- and weight-matched groups of amiodarone-treated patients with type 2 diabetes: patients with treated overt hypothyroidism (group I, n=15), patients with untreated subclinical hypothyroidism (group II, n=15), and subjects without thyroid disorders (group III, n=18). The lipid profile, fasting plasma glucose levels, the homeostatic model assessment 1 of insulin resistance ratio (HOMA1-IR), glycated hemoglobin, the estimated glomerular filtration rate, as well as serum levels of thyrotropin, thyroid hormones, prolactin, insulin and insulin-like growth factor-1 (IGF-1) were assessed at baseline and after 6 months of metformin treatment (2.55-3g daily).


RESULTS
In all groups of patients, metformin reduced plasma glucose and triglycerides, serum insulin, glycated hemoglobin as well as HOMA1-IR. The estimated glomerular filtration rate, thyroid hormones, prolactin and IGF-1 remained at a similar level throughout the study. In patients with untreated amiodarone-induced hypothyroidism, but not in the other groups of patients, metformin reduced serum levels of thyrotropin and this effect correlated weakly with its action on insulin sensitivity.


CONCLUSIONS
The obtained results indicate that the effect of metformin on hypothalamic-pituitary-thyroid axis activity is partially related to thyroid function. Metformin treatment may bring clinical benefits to patients with amiodarone-induced hypothyroidism and poor tolerance of exogenous L-thyroxine.
['Krysiak|Robert|R|', 'Gilowska|Małgorzata|M|', 'Szkróbka|Witold|W|', 'Okopień|Bogusław|B|']
D000368:Aged D000638:Amiodarone D003924:Diabetes Mellitus, Type 2 D005260:Female D006801:Humans D007030:Hypothalamo-Hypophyseal System D007037:Hypothyroidism D007328:Insulin D007333:Insulin Resistance D007334:Insulin-Like Growth Factor I D008297:Male D008687:Metformin D008875:Middle Aged D011388:Prolactin D013961:Thyroid Gland D013972:Thyrotropin D013973:Thyrotropin-Releasing Hormone D013974:Thyroxine
Metformin Hypothalamic-pituitary-thyroid axis Amiodarone Diabetes mellitus