Thyroid Study Type 2 Diabetes Mellitus (T2DM)
Thyroid Study Type 2 Diabetes Mellitus (T2DM)
Background of the study:

 Thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are known to promote weight loss,
 which could be beneficial for treating obesity, and type 2 diabetes. Thyroid hormone
 treatment stimulates energy expenditure resulting in increased body heat production, in which
 brown adipose tissue play an important role. It is hypothesized that thyroid hormones would
 induce increased energy expenditure via a process called mitochondrial uncoupling, thereby
 creating an inefficient energy status. Indeed, an in vivo study showed a 70% increased flux
 through the tricarboxylic acid cycle (TCA) and an unchanged ATP synthesis rate upon T3
 treatment in lean, healthy young men. The disproportionate increase in TCA flux compared with
 ATP synthesis suggests increased mitochondrial uncoupling. It is however unknown whether
 increased mitochondrial uncoupling would increase fat oxidation and exerts favorable effects
 on insulin sensitivity. There is compelling evidence that type 2 diabetic patients have high
 levels of fat accumulation in non-adipose tissues, such as skeletal muscle, heart and liver.
 Ectopic fat accumulation is related to insulin resistance, however, why this fat accumulates
 in peripheral organs is not known. Recently, studies reported compromised mitochondrial
 oxidative capacity in type 2 diabetic patients and first-degree relatives of diabetic
 patients, suggested to play an important role. Therefore, subjects suffering from overweight
 and/or type 2 diabetes with overt hypothyroidism form an interesting group for examining the
 metabolic effects of thyroid hormone treatment, as less is known about the effects of thyroid
 hormone treatment in these groups.

 Objective of the study:

 The purpose of this study is to evaluate whether thyroid hormone replacement therapy in type
 2 diabetic patients suffering from overt hypothyroidism, will improve muscular mitochondrial
 function, lower ectopic fat accumulation in muscle and liver, increase brown adipose tissue
 activity and enhance insulin sensitivity.

 Study design:

 Type 2 diabetic patients diagnosed with hypothyroidism will undergo 3 months of thyroid
 hormone replacement therapy (THRT) (Euthyrox®, Merck, Germany). Patients will be
 metabolically characterized (such as insulin sensitivity and fat accumulation in peripheral
 tissues) before and after this thyroid hormone replacement therapy.

 Study population:

 17 type 2 diabetic patients diagnosed with overt hypothyroidism (9 from the Netherlands, 8
 from Germany which will only do the PET-CT)

 Primary study parameters/outcome of the study:

 Thyroid hormone-induced change in whole body insulin sensitivity (change in
 insulin-stimulated glucose disposal) and muscle mitochondrial function.

 Secondary study parameters/outcome of the study (if applicable):

 Thyroid hormone-induced change of lipid content in skeletal muscle and liver and brown
 adipose tissue activity.
Inclusion Criteria:

 -  Male or postmenopausal females

 -  Age 40-65 years

 -  Body mass index (BMI) < 40 and > 27 kg/m2

 -  Stable dietary habits (no weight loss/gain >3 kg in the last 6 months)

 -  Stable physical activity levels for at least six months

 -  Newly diagnosed hypothyroid, non-insulin dependent type 2 diabetic patients having TSH
 values higher then > 4.0 mU/l and lowered concentrations of free T4 < 8.0 pmol/l.

 -  Type 2 diabetic patients using sulphonylurea and or metformin therapy for at least six
 months with a constant dose for at least two months.

 -  Hypothyroid diabetic patients due to Hashimoto disease (TPO > 100 IE/ml; Tg > 344
 IE/ml), should have no auto-antibodies against glutamic acid decarboxylase (GAD), IA-2
 and insulin to exclude type 2 polyglandular autoimmune syndrome (PGAII) (to exclude
 type 1 diabetes).

 -  Type 2 diabetic patients should have a HbA1c level < 8.0%

 -  Type 2 diabetic patients will be included when having no diabetes-related
 co-morbidities like cardiovascular diseases, diabetic foot, polyneuropathy,
 retinopathy.

 Exclusion Criteria:

 -  Unstable body weight

 -  Participation in an intensive weight-loss program or vigorous exercise program during
 the last year before the start of the study

 -  Medical history including active cardiovascular disease, i.e. history of coronary
 artery disease (i.e. history of angina pectoris, percutaneous transluminal coronary
 angioplasty or coronary artery bypass grafting) or cardiac arrhythmias.

 -  Liver disease or liver dysfunction (ALT>2.5 x increased)

 -  Impaired renal function (creatinine > 120 umol/L)

 -  Systolic blood pressure >160 mmHg or diastolic blood pressure >100 mmHg

 -  Hb <7.4 mmol/l (12 g/dl) in women, and <8.1 mmol/l (13 g/dl) in men

 -  Abuse of drugs and/or alcohol

 -  Contraindications for MRI scanning (please see appendix III: MRI contraindication
 questionnaire)

 -  Patients with history of thyroid cancer

 -  Patients using α and/or β blockers

 -  Severe diabetes which requires application of insulin or patients with
 diabetes-related complications

 -  History of psychiatric disease

 -  Diabetes related co-morbidities like cardiovascular diseases, diabetic foot,
 polyneuropathy, retinopathy.

 -  Use of medications known to interfere with glucose homeostasis (i.e. corticosteroids,
 thiazolidinediones)

 -  Hypothyroid diabetic patients due to Hashimoto disease with positive test values for
 auto-antibodies against GAD, IA-2 and insulin to exclude type 1 diabetes.

 -  Use of anticoagulants, other than platelet aggregation inhibitors.

 -  Patients that have donated blood in the past 6 months