- Pathophysiology of T4 secretion: TSH secreted in the anterior pituitary and stimulates the TSH receptor in the thyroid to secrete thyroid hormone
- Clinical presentation of Hyperthyroidism: Hyperdefecation (not diarrhea), osteoporosis, oligomenorrhea in pre-menopausal females, hair changes, palpitations, arrhythmias
- Etiologies of hyperthyroidism
- Grave’s Disease (most common cause of hyperthyroidism)
- Destructive thyroiditis (subacute, silent, postpartum)
- Multinodular Goiter/Toxic Adenoma
- Medication-induced (amiodarone, lithium, IFN-a, etc)
- Factitious
- Antibodies
- Anti-TPO and anti-thyroglobulin Ab seen with Hashimoto’s Disease (hypothyroidism)
- TSI (thyroid stimulating immunoglobulin) and TBII associated with Graves Disease.
- TSI binds to TSH receptors on thyroid gland, stimulating production of thyroid hormone.
- TSI also binds to TSH receptors located on fibroblasts, stimulating proliferation and glycosaminoglycan production in retro-orbital space.
- Clinical Presentation specific to Graves include pretibial myxedema (5% patients with Graves), exophthalmos (25% of patients with Graves)
- Work-up of Hyperthyroidism
- If evidence for Graves Disease, then GD likely diagnosis.
- Evidence of nodules on physical Exam:
- If None: Perform RAI uptake scan and antibody studies.
- If increased uptake, elevated thyroid hormone due to over-synthesis
- If diffuse uptake, think Graves Disease
- If patchy uptake, think toxic multinodular goiter
- If decreased uptake, think of factitious or destructive causes (subacute, silent, postpartum.
- If increased uptake, elevated thyroid hormone due to over-synthesis
- If Present: Get RAIU scan and thyroid ultrasound to distinguish TNG vs TA and/or evidence of cold nodules. Check for any concerning factors for thyroid cancer.
- If None: Perform RAI uptake scan and antibody studies.
- Thyroglobulin: Precursor to thyroid hormone production. Combined with iodine to produce T4.
- May be used to differentiate factitious vs destructive thyroiditis, surveillance for thyroid cancer.
- Treatment Options:
- Thionamides – Methimazole versus PTU
- Watch for drug rash and/or agranulocytosis
- Radioactive iodine ablation
- Do not use in patients with Graves Disease with severe ophthalmopathy as this can worsen symptoms.
- Surgery
- Thionamides – Methimazole versus PTU
| Grave’s Disease | Multinodular Goiter | Subacute Thyroiditis | |
| Clinical Course/Exam
|
Exophthalmos
Pre-tibial Myxedema |
Hyperthyroid symptoms
Palpable nodules |
Preceded by URI sx, Pain around the neck, pain with palpation, initially hyperthyroid (6 weeks) but progresses to hypothyroid (6 weeks), then normalizes |
| Diagnosis Tests
|
Low TSH
High Free T4 TSI RAIU |
TSH/T4
RAI Thyroid US |
TSH, Free T4
RAI – low uptake Thyroid US – diffuse enlargement |
| Treatment
|
PTU
Methimazole (don’t use in 1st trimester of pregnancy). Watch for agranulocytosis. RAIA, then will require Surgical. Don’t use RAIA for patients with exophthalmos. |
If compressive sx (dysphagia, etc) then surgery
If no compressive symptoms, can treat with RAIU. Toxic patients can also be treated with thionamides |
NSAIDS, supportive
Then Prednisone if poor response Symptomatic treatment, such as propranolol or beta blockers Thionamides not indicated |
SCVMC IM Chief Resident Blog 