Mechanistic Study of Subclinical Hypothyroidism In the Elderly
Mechanistic Study of Subclinical Hypothyroidism In the Elderly
Subclinical hypothyroidism, defined as an elevated TSH in the setting of normal thyroid
 hormone levels, is a common diagnosis in the elderly. The purpose of this study is to examine
 the hypothalamic-pituitary-thyroid axis in men and women aged 70 years and older with
 persistent subclinical hypothyroidism. To evaluate the mechanism behind this condition,
 participants will undergo thyrotropin releasing hormone stimulation testing at 3 visits:
 baseline and while taking two different thyroid hormone preparations, levothyroxine and
 liothyronine. The investigators will also assess physiologic responses to these two different
 thyroid hormone medications to help us understand how the thyroid works in advanced age.
Inclusion Criteria:

 1. men and women aged 70 and older

 2. TSH between 4.5 and 19.9 mU/L as an outpatient

 3. ability to provide informed consent

 Exclusion Criteria:

 Laboratory Tests:

 1. TSH <4.5 mU/L or >20 mU/L on repeat testing at least four weeks later or free T4 level
 outside the reference range

 2. thyroid peroxidase (TPO) antibody positive

 3. abnormal liver function tests (LFTs >3 x upper limit of normal)

 4. hemoglobin <11 g/dL

 Surgeries or Procedures:

 1. thyroid surgery

 2. pituitary surgery

 3. bariatric surgery

 4. bowel resection involving the jejunum and upper ileum

 5. radioactive iodine therapy

 6. radiation treatments to head or neck

 Medical Conditions:

 1. diagnosis of pituitary disease

 2. diagnosis of amyloidosis, sarcoidosis, hemochromatosis

 3. diagnosis of adrenal insufficiency

 4. obesity with BMI > 35 mg/kg2

 5. history of stroke

 6. chronic or ongoing angina, Class II or higher congestive heart failure, or
 uncontrolled hypertension with current blood pressure greater than 160/100

 7. diabetes mellitus with hemoglobin A1C level greater than 8.0% in the past six months

 8. celiac sprue, Crohn's disease, ulcerative colitis, Zollinger-Ellison syndrome

 9. renal insufficiency with calculated glomerular filtration rate <45 cc/min

 10. cognitive impairment with Mini Mental State Exam[30] <24/30

 11. history of any seizures

 12. unstable medical or psychological condition in the judgment of the principal
 investigator

 Medications:

 1. thyroid hormone preparations

 2. antithyroid drugs

 3. medications that interfere with the absorption or metabolism of thyroid hormone

 4. medications that interfere with the TRH stimulation test

 5. proton pump inhibitors