FGF-21 Levels and RMR in Children and Adolescents With Hashimoto's Thyroiditis (THYROMETABOL)
FGF-21 Levels and RMR in Children and Adolescents With Hashimoto's Thyroiditis (THYROMETABOL)
Thyroid hormone (TH) and fibroblast growth factor 21 (FGF-21) are reported to share common
 metabolic pathways and underlying mechanisms in terms of energy balance, thus affecting both
 thermogenesis and resting metabolic rate (RMR). Although FGF-21 levels has been studied in
 children and adolescents regarding obesity, body composition and insulin resistance, data in
 children and adolescents diagnosed with Hashimoto's thyroiditis are lacking. Therefore, the
 purpose of this study is to measure the RMR in children and adolescents diagnosed with
 clinical hypothyroidism due to thyroiditis Hashimoto just before starting levothyroxine
 treatment and after six months achieving an euthyroid state, and to detect any association
 between serum FGF-21 levels and RMR.
Patients with hypothyroidism due to Hashimoto thyroiditis (HT) will receive standard
 treatment with levothyroxine by their attending physician in order to achieve an euthyroid
 status. Free T4 level is expected to be displayed within normal range (10-16 mg/dl) after the
 first few months of levothyroxine administration, and TSH level is expected to be less than
 5mU / ml after 3-4 months. Participants will be re-examined in 6 months after the initiation
 of substitution pharmacotherapy with levothyroxine. Similarly, a control group consisted by
 healthy children and adolescents matched for age and gender will be re-examined after a 6-
 month interval from the initial measurements.

 From all participants detailed medical history will be recorded and following parameters will
 be measured and calculated: Age and pubertal stage according Tanner, height, body weight,
 Body Mass Index (BMI),waist circumference, hip circumference, Mid Arm Circumference (MAC),
 skinfolds measurement (using a Harpenden skinfold caliper), in order to estimate the
 percentage (%) body fat. Measurement of RMR, with a portable device applying indirect
 calorimetry (Fitmate Cosmed, Italy) The blood samples will be collected and centrifuged
 immediately after the RMR measurement. Following parameters will be tested in serum: FGF-21
 (measured by ELISA method), TSH, F-T3, F-T4, TPOAb, TgAb, Fasting Glucose, Insulin, TChol,
 TG, HDL, LDL, AST, ALT, γGT (applying automatic chemical analyzers and analogues reagents
 that already exist at the Hospital).

 Additionally, a 3-day food dairy (two weekdays and one weekend day) will be completed by the
 participants and/or their caregivers just a week before the measurement of the RMR and the
 blood sampling.
Inclusion Criteria:

 For patients

 -  Subjects 5 to 18 years old.

 -  First diagnosis of hypothyroidism due to Hashimoto's thyroiditis (high levels of serum
 antithyroid autoantibodies (antiTPO, anti-TgAb).

 For Controls:

 -  Healthy individuals 5 to 18 years old.

 -  BMI for age between 15th and 85th percentile (z-score between -1 and +1).

 Exclusion Criteria:

 For patients

 -  Presence of euthyroidsm, subclinical hypothyroidism, hyperthyroidism.

 -  Pre-existing medical treatment for clinical hypothyroidism.

 -  Taking other medications (eg growth hormone, corticosteroids) in the last 3 months.

 -  Taking food supplements (eg omega-3 fatty acids, amino acids) in the last 3 months.

 -  Concomitant endocrine, metabolic, degenerative and / or chronic diseases other than
 obesity (eg diabetes, hyper / hypo-cortisolemia, cardiovascular diseases, kidney
 diseases, myasthenia, neurological diseases, psychiatric disorders eg anorexia
 nervosa, cancer, anemia, celiac disease, chromosomal abnormalities eg syndrome Turner,
 Down, etc).

 -  Participation in any daily organized physical activity (sport), more than 1 hour per
 day.

 -  Presence of menstrual disorders in adolescent girls.

 -  Having any kind of nutrition/dietary intervention (eg weight loss diet, hypocaloric,
 ketogenic, low-protein diet), in the last 6 months.

 For Controls:

 -  Presence of any form of thyroid disease.

 -  Presence of any endocrine, metabolic, degenerative and / or chronic disease (eg
 diabetes, hyper/ hypo-cortisolemia, obesity, metabolic syndrome, cardiovascular
 diseases, kidney diseases, myasthenia, neurological diseases, psychiatric disorders eg
 anorexia nervosa, cancer, anemia, celiac disease, chromosomal abnormalities eg
 syndrome Turner, Down, etc).

 -  Taking any medication (eg growth hormone, corticosteroids) in the last 3 months.

 -  Taking food supplements (eg omega-3 fatty acids, amino acids) in the last 3 months.

 -  Participation in any daily organized physical activity (sport), more than 1 hour per
 day. Presence of menstrual disorders in adolescent girls.

 -  Having any kind of nutrition/dietary intervention (eg weight loss diet, hypocaloric,
 ketogenic, low-protein diet), in the last 6 months.