Endocrinology Flashcards
What is the pathophysiology of Graves Disease
Autoimmune disorder in which IgG antibody binds to the TSH receptor and triggers synthesis of excess thyroid hormone
What does a radioiodide scan show in Graves Disease?
Diffuse uptake because every thyroid cell is hyperfunctioning
What is Plummer Disease
AKA Toxic Multinodular Goiter. It’s when there are discrete areas of hyperfunctioning thyroid gland.
What does a radioiodide scan show in Plummer Disease?
Patchy uptake
What are 2 causes of transient hyperthyroidism?
Hashimoto’s Thyroiditis, Subacute (Granulomatous) Thyroiditis
What are the three signs of hyperthyroidism that are specific to Grave’s Disease?
- Exophthalmos
- Pretibial Myxedema
- Thyroid Bruit
What do you find on exam in subacute thyroiditis?
An exquisitely tender, diffusely enlarged gland with a viral illness.
What is the mechanism of the development of exophthalmos?
There is edema of the extraocular muscles and retro-orbital tissues.
What is the mechanism of the development of pretibial myxedema?
Edema over the tibial surface due to the accumulation of mucopolysaccharides in the dermis.
What situations cause an increase in TBG?
- Pregnancy
- Liver disease
- OCP use
- Aspirin
For patients on thyroid medication, what should you monitor and why?
You should monitor the leukocyte count because they can cause agranulocytosis.
What are the shared side effects of Methimazole and PTU?
-Rash, agranulocytosis, hepatotoxicity, arthralgias
What is the MOA of PTU?
Inhibits thyroid hormone synthesis and inhibits the peripheral conversion of T4 to T3.
What is the MOA of Methimazole?
Inhibits thyroid hormone synthesis
What are some complications of thyroid surgery?
- Permanent hypothyroidism
- Accidental hypoparathyroidism (look for hypocalcemia)
- Recurrent laryngeal nerve palsy
How do you treat pregnant patients with Graves Disease?
PTU
What are some precipitants of thyroid storm?
- Stress (trauma, surgery, childbirth, illness)
- Infection
- DKA
What are the clinical manifestations of thyroid storm?
- Marked fever
- Tachycardia
- GI upset (N/V/D)
- Agitation or psychosis
- Confusion
How do you treat thyroid storm?
- Supportive: IV fluids, cooling blankets, glucose
- PTU every 2 hours
- Beta blockers to control heart rate
- Dex to impair peripheral generation of T3 from T4 and to provide adrenal support.
What are patients with hashimotos at increased risk for?
-Increased risk for thyroid carcinoma and thyroid lymphoma
What are the risk factors for thyroid cancer?
- Head and neck radiation
- Gardner Syndrome and Cowden syndrome for papillary cancer
- MEN type II for medullary cancer
What is the most important risk factor for papillary carcinoma?
History of radiation to the head and neck
Which thyroid cancer has the best prognosis?
Papillary carcinoma
How does papillary carcinoma spread?
via the lymphatics. Distant mets are rare.
What is the prognosis for Follicular Carcinoma
Has a worse prognosis than papillary carcinoma. It spreads early via hematogenous spread and there may be distant mets in up to 20% of cases.
How do you diagnose follicular carcinoma?
You MUST doe a fine needle biopsy because tumor extension through the tumor capsule or vascular invasion distinguishes it from a benign adenoma.
What is Hurthle Cell Carcinoma?
Variant of follicular carcinoma. It has characteristic cells containing abundant cytoplasm, tightly packed mitochondria, and oval nuclei with prominent nucleoli. These tumors do not take up iodine.
If you have a patient with medullary carcinoma, what should you also screen for and why?
Screen for pheochromocytoma because 1/3 of medullary carcinomas are associated with MEN II.
What cells do medullary carcinoma arise from?
Parafollicular C Cells.
What do parafollicular C cells produce?
Calcitonin, therefore you expect it to be high in medullary carcinoma.
What is the prognosis of anaplastic carcinoma?
It is the worst. Death typically occurs within a few months. Mortality is usually due to invasion of adjacent organs (trachea, neck vessels etc).
What are some exam findings that suggest malignancy of the thyroid?
- Fixed nodule, no movement on swallowing
- Firm consistency or irregular
- Solitary nodule
- Hx of radiation to the neck
- Hx of rapid development
- Vocal cord paralysis (recurrent laryngeal nerve paralysis)
- Cervical adenopathy
- Elevated serum calcitonin
- Fam hx of thyroid cancer.
What is the initial test of choice for evaluation of a thyroid nodule?
-Fine Needle Aspiration
Which cancer is FNA not reliable for?
Follicular. You need surgery because histology does not differentiate between benign and malignant follicular cells.
When do you perform a thyroid scan after FNA?
If the FNA is indeterminate or if patients have a low TSH since they are more likely to have a hyperfunctioning nodule.
Which nodules are more likely to be malignant?
Cold, meaning they are hypofunctional and don’t have as much uptake.
What is the cause of subacute thyroiditis and what HLA is it associated with?
- Usually follows a viral illness
- Associated with HLA-B35
Describe the clinical course of subacute thyroiditis
- Prodrome for about 2 weeks with fever or flu-like illness
- May have transient hyperthyroidism due to leakage of hormone from an inflamed thyroid gland. This is followed by a euthyroid state, then a hypothyroid state as hormones are depleted
- Painful tender thyroid gland that may or may not be enlarged.
How do you diagnose subacute thyroiditis?
- Radioiodine uptake is low
- Low TSH secondary to suppression with T3/T4
- High ESR
What is the treatment for subacute thyroidits?
NSAIDs and aspirin. May use corticosteroids if more severe pain. Pt usually resolves within a few months to a year.
Describe the pathology of Fibrous Thyroiditis/Reidel Thyroiditis?
There is fibrous tissue deposition that replaces normal thyroid tissue, leading to a FIRM thyroid. Patients may be hypothyroid.
What is the difference between subacute viral thyroiditis and subacute lymphocytic thyroiditis?
Subacute lymphocytic thyroiditis does NOT have pain or tenderness of the thyroid gland.
Descibe the clinical course of subacute lymphocytic thyroiditis
There is a transient thyrotoxic phase of 2-5 months that may be followed by a hypothyroid phase. The hypothyroid phase is usually self limited and may be the only manifestation of the disease.
Describe the clinical manifestations of Hashimoto’s Disease.
- Goiter, most common feature
- Slow decline in thyroid function
How do you make the diagnosis of Hashimoto’s
- May be hypothyroid
- Antiperoxidase antibodies
- Antithyroglobulin antibodies
- Antimicrosomal antibodies
- Irregular distribution of iodine on the thyroid scan
Treatment of Hashimoto’s
Thyroid hormone to achieve a euthyroid state
What are the two most common causes of hypothyroidism?
- hashimoto’s thyroiditis
- Iatrogenic hypothyroidism (radiation, thyroidectomy, medications like lithium or amiodarone)
What lab values are seen in secondary or tertiary hypothyroidism, with respect to TSH and T4
Both TSH and T4 levels would be low
Would you expect LDL to be elevated or low with hypothyroidism? What about HDL?
Elevated LDL
Low HDL
What is a myxedema coma?
A rare condition that presents with a depressed state of consciousness, profound hypothermia and respiratory depression.
How do you treat myxedema coma?
Supportive care, IV fluids, IV thyroxine, and hydrocortisone, maintain BP
What is the most sensitive indicator of hypothyroidism?
High TSH
Size of a microadenoma
<10 mm
Size of a macroadenoma
> 10mm
What is the most common type of a pituitary adenoma?
A prolactinoma. Also the most common cause of hyperprolactinemia.
What are some causes of hyperprolactinemia?
- Pituitary adenoma
- Medications
- Pregnancy
- Renal failure
- Suprasellar mass lesion
- Hypothyroidism
- Idiopathic
What are some medications that can cause hyperprolactinemia?
- Antipsychotic medications like risperidone
- H2 blockers
- metoclopramide
- verapamil
- estrogen
What are some signs and symptoms of hyperprolactinemia in men?
- Decreased libido
- Hypogonadotropic hypogonadism
- Infertility
- Impotence
- Galactorrhea or gynecomastia
- Visual field defects and headaches
What are some signs and symptoms of hyperprolactinemia in women?
- Premenopausal menstrual irregularities
- Anovulation and infertility
- Decreased libido
- Dyspareunia or vaginal dryness
- Osteoporosis
- Galactorrhea
- Visual field defects and headaches
Why does hyperprolactinemia cause hypogonadism?
Elevated levels of prolactin inhibit secretion of GnRH and therefore there is less release of LH and FSH and inhibiting production of testosterone and estrogen.
Describe the workup for hyperprolactinemia symptoms
- Get a prolactin level
- Pregnancy Test
- TSH level (elevated TRH can cause prolactin release)
- MRI or CT
What is the medical treatment for prolactinomas?
Bromocriptine or cabergoline. Both are dopamine agonists. Remember that dopamine inhibits prolactin release.
What is the most common cause of death in patients with acromegaly?
Cardiovascular disease (cardiomegaly)