Patient description: The patient is a 33-year-old woman complained of fatigue, weight gain and abnormal spotting between menses. No hirsutism or nipple discharge was detected. Her BMI was 34. Her lab results were remarkable for high TSH level (13 mU/L) and low free T4 level (0.2 ng/dl). Her anti-TPO levels were extremely high (120 IU/ml). She was diagnosed with Hashimoto's thyroiditis. Her aunt, brother and mother have the same disease. After starting 250 mcg Levothyroxine per day, her symptoms improved significantly and her periods are normal. She is still overweight with BMI of 31. Her most recent thyroid profile revealed all results except for anti-TPO within the normal range: TSH: 2.35 mU/L Free T4: 2.7 ng/dl Anti-TPO: 75 IU/ml

Clinical trial eligibility criteria: eligible ages (years): 18.0-65.0,  Thyroid Diseases Age greater than or equal to 18 years, male or female. History of total or near total thyroidectomy or hypothyroidism on replacement therapy. For non-thyroidectomized patients, at least three-year history of replacement therapy (at least 1.2 mcg/Kg LT4/body weight), and less than 5% uptake at 24H on (123)I thyroid scan while on replacement therapy. Written informed consent  BMI less than or equal to 20 or greater than or equal to 30 kg/m(2). Metastatic thyroid cancer or history of thyroid cancer with high risk of recurrence requiring suppressive thyroid hormone therapy (Singer 1996). Significant thyroid residual greater than 1 mL as measured by ultrasound (limited to thyroidectomized patients) or greater than 5 percent uptake at 24H on (123)I thyroid scan while on replacement therapy (limited to hypothyroid patients not undergone total thyroidectomy). History or symptoms compatible with cardiovascular disease, including paroxysmal supraventricular tachycardia, atrial fibrillation, syncopal episodes or use of prescription medications for heart conditions, including antihypertensives. Allergy to lidocaine, isoproterenol, TRH, levothyroxine, liothyronine, Tylenol #3, oxycodone, nitroglycerin. Pregnancy or unwillingness to use non-hormonal contraception during the study. Breastfeeding Use of hormonal contraceptives or estrogen replacement therapy. Use of tobacco (smoking, chewing) for the two weeks preceding the hospital admissions (metabolic testing) Diabetes mellitus, either type I or II. Hypercholesterolemia (serum levels greater than or equal to 240 mg/dL), hypertriglyceridemia (plasma levels greater than or equal to 220 mg/dL) and/or use of antilipemic therapy. Liver disease or ALT serum level greater than two fold the upper laboratory reference limit. Renal insufficiency or estimated creatinine clearance less than or equal to 50 mL/min. Use of medications/supplements/alternative therapies known to alter thyroid function. Current history or symptoms compatible with psychosis including major depression (including history of hospitalization for depression, history of attempted suicide, history of suicidal ideation). Use of antipsychotic medications History of drug or alcohol abuse within the last 5 years; current use of drugs or alcohol (CAGE greater than 3). Keloid formation (relative to skeletal muscle and subcutaneous adipose tissue biopsies). Current or previous clinically significant (requiring medical/surgical intervention) extrathyroidal manifestations of autoimmune thyroid disease (dermopathy, ophthalmopathy, arthropathy)