Describe the hypothalamic-pituitary-thyroid axis.

G.B. is a 50-year-old female patient presenting with a 9-month history of ongoing weight gain, cold intolerance, fatigue, constipation, depression, and memory loss. She states her appearance is changing with very dry skin, hair loss, and a hoarse voice. Temperature 96.4 degrees F, heart rate at 56, BP 100/60. Obese female in no acute distress who speaks slowly but is alert and oriented x3. Has a puffy face, skin cool/dry, and thickened on lower extremities. The thyroid gland is not palpable. Neurological exam is intact except for delayed deep tendon reflexes bilateral upper and lower extremities. CBC and differential, along with chemistry panels, are within normal limits. Serum Free T4 is 3.8 mcg/dl, TSH is .8u/U/ml, and total serum cholesterol is 255. Despite this laundry list of history that can lead to a variety of differential diagnoses (hypothyroidism): • What do your clinical exam and laboratory findings indicate? • What is happening at the cellular level to cause these physical changes? • What might be the cause of the systemic disease? • Describe the hypothalamic-pituitary-thyroid axis. • Is this primary or secondary hypothyroidism? • What would the treatment be targeted at? • If she were to have hyperthyroidism during your care, what would those symptoms look like?