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

A 2-years prospective, randomized and multicentric study will be performed to assess the efficacy of metformin compared to sitagliptin on benign thyroid nodules size ≥ 2 cm, in newly diagnosed patients with type 2 diabetes.

Previous studies reported that prevalence of thyroid nodules (TN) is increased in patients with insulin resistance (IR) and type 2 diabetes mellitus (T2DM). However, there are no guidelines for the management of TN in this target population. In 2013, the French National Health Insurance reported that thyroid surgery procedures for benign nodules have increased unjustifiably. The impact of such surgery on the patients could be serious, with psychological repercussions and risks of surgical complications and the need of a substitutive lifetime hormonal treatment. The investigators hypothesize that metformin may reduce the need of TN surgery by decreasing benign TN size through a reduction of IR profile. A 2-years multicentric prospective study will be conducted to compare efficacy of metformin versus sitagliptin on benign thyroid nodules size in patients with initial benign thyroid nodules ≥ 2 cm. The percentage of thyroid surgery avoided, IR profile measured by Homeostasis Model Assessment of Insulin Resistance-Index (HOMA-IR-index) and adipokines concentrations will be also collected at inclusion ad at 2 years. The Primary outcome will be the percentage of patients in each group who had at least a 20% decrease in one or more nodules of more than 2 cm at 2 years. Several secondary outcomes will be registered: percentage of thyroid surgery observed in each group at 2 years, number of new TN (≥ 10mm) after 2 years of follow-up , percentage of metabolic syndrome before and after treatment, proportion of subjects with improvement of the HOMA-IR index and adipokine concentrations, plasmatic thyroid-stimulating hormone (TSH), T4 and T3 levels evolution, percentage of insulin like growth factor-1 (IGF-1) and adiponectin receptor expression in thyroid tissues after TN surgery.

Eligibility Criteria:
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