Efficacy of Metformin Versus Sitagliptin on Benign Thyroid Nodules in Type 2 Diabetes

Inclusion Criteria:

* Patients with T2DM aged 18 to 65 years;
* Uncomplicated T2DM, evolving for less than 3 years;
* Patients with HbA1c levels between 7 and 8% (after the run-in period)
* Patients with at least one TN ≥ 2 cm non-cystic, whose benignity will be confirmed by a fine-needle aspiration cytology performed twice regardless of ultrasound TIRADS score;
* Naive subjects of any treatment: never received an anti-diabetic treatment OR received an anti-diabetic treatment of less than 30 days since diagnosis OR did not receive an anti-diabetic treatment during the 30 days before screening;
* Patients with a creatinine clearance \> 60 ml/min;
* Informed and written consent signed by the patient and the investigator;
* Affiliation to the national social health system or equivalent.

Exclusion Criteria:

* Subjects without adequate or impaired decisional abilities for consent to research and placed under guardianship, trusteeship or safeguard of justice
* Pregnant or breastfeeding woman
* Woman of childbearing potential without effective contraception (estroprogestative, presentative, intrauterine device)
* Suspect thyroid nodules in ultrasound (TIRADS 4 to 5) with confirmation after a fine-needle aspiration cytology;
* Thyroid function abnormalities or a history of thyroid disease;
* Thyroid nodules whose size or symptoms (compressive signs) require surgery
* Ioduria \<100ug /L
* Thyroid autoimmunity: positive anti-peroxidase, thyroglobulin or anti-TSH receptors antibodies
* Levothyroxine treatment
* History of cervical radiotherapy or thyroid surgery
* Type 1 diabetes
* Insulin deficiency
* History of hypersensitivity to one of the active substances
* History of pancreatitis
* Obesity linked to endocrine disease
* Presence of severe complications of T2DM (ischemic heart disease, heart failure with reduced left ventricular ejection fraction, severe lower extremity arteritis, gangrene, retinopathy, end-stage renal failure, cerebrovascular accident)
* HbA1c levels \> 8% after the run-in period
* Liver diseases (liver failure, cirrhosis, viral hepatitis B or C)
* Acute alcoholic intoxication, chronic alcoholism
* Psychiatric diseases (depression, schizophrenia)
* Neurological diseases (epilepsy, demyelinating diseases, etc.)
* Treatment influencing the morphology or thyroid function: corticosteroids, lithium, iodized products etc. ...
* Acute conditions that may impair renal function such as: dehydration, severe infection, shock
* Respiratory failure
* Metabolic acidosis