This project has the following primary aims:

To measure changes in appetite and food intake in newly diagnosed hypothyroid patients during the first six months after starting levothyroxine (L-T4) substitution therapy

Secondary aims are:

To delineate the effect of L-T4 substitution therapy on thyroid status, body weight, body mass index (BMI), body composition, physical activity, glycaemic control, postprandial gut and pancreatic hormone responses, gastric and gall bladder emptying, resting energy expenditure (REE), quality of life (QOL) and cognitive function

18 newly diagnosed hypothyroid female patients and 18 healthy controls age between 20 and 75 years will be recruited from the out-patients clinic in Herlev and Gentofte Hospital and the general practitioners before start of substitution therapy.

The study is devided in to three identical experimental days of approx. 6 hours. First experimental day placed before T4 treatment is initiated. Second day as soon as Thyroid Stimulating Hormone (TSH) is below 4 milli unit pr liter (mU/l). The Third experimental day after 6 months of T4 therapy.

For 5-7 days before each experimental day, the participants' physical activity energy expenditure (PAEE) will be monitored by an Actiheart® pedometer attached to the skin of the chest.

The last two days before each experimental day, the participants will follow a standardised diet following World Health Organization guidelines on energy requirements and nutrient composition according to gender, age and body weight Shortly after diagnosis patients will undergo a test panel at the first experimental day, where patients arrives fasting.

Visual analog score on satiety and thirst will be filled out continuously. REE will be measured by a CCM-express calorimeter,

• Dual Energy X-ray absorptiometry (DEXA)-scan
• Blood samples will be taken continuously during the experimental day. Gall bladder size will be examined at 6 times during the experimental day using ultra sound.

At the end of the day, patients´ satiety will be examined with an ad libitum meal.

Blood will be analysed for Gastric inhibitory polypeptide (GIP), Glucagon-like Peptide 1 (GLP-1), Glucagon-like Peptide 2 (GLP-2), glucagon, peptide tyrosine tyrosine (PYY), Gastrin, Cholesystokinin (CCK), Insulin, C-peptide, Blood sugar, Cholesterol, Free fatty acids and paracetamol.

Inclusion Criteria:

• TSH > 10
• Female

Exclusion Criteria:

• Competing serious disease
• Male
• Not able to understand written and spoken danish
• Pregnancy
• Thyroidectomized patients
• Amiodarone treatment.

18 Hypothyroid female patients with a TSH > 10 without Levothyroxine treatment.