Lecture 6: Thyroid and Parathyroid Disorders Flashcards
If serum values of Ca2+ and PO4 are moving in the same direction (i.e., both ↓) this tell you that the problem is related to what?
Vitamin D
If calcium is high, but PTH is low, what are some of the underlying causes you need to investigate?
- Malignancy + Metastasis + Lymphoma
- Granulomatous disease
- Drugs
- Multiple myeloma
- Vit D intoxication
Polyuria + dehydration + renal impairment are associated with (chronic or acute) development of hypercalcemia?
Acute
Which medication should be used in a patient with chronic hypercalcemia who has developed HTN?
Loop diuretics —> ↓ serum [Ca2+] and ↓ BP
If you suspect a vitamin D deficiency in a patient with ↓ Ca2+ and ↓ PO4, which form of vitamin D should you order a test for, why?
- 25-OH Vitamin D = the storage form; important to check how depleted the pt is
- 1,25-OH Vit D the active form should also be checked
What’s the formula for corrected calcium when albumin is low?
Cacorrected= measured Ca2+ + 0.8 (4.0 - serum albumin)
What would you expect the serum and urine calcium levels to be like in someone who is bed ridden and has normal kidney function?
- Serum levels will likely be normal
- Urine levels will be elevated = hypercalciuria
- Due to ↑ osteoclast activity causing ↑ Ca2+ in blood and suppression of PTH from the high Ca2+ –> normal renal function maintains homeostasis
What is responsible for the hydroxylation of 25-OH vitamin D to 1,25-OH vitamin D?
PTH
What is a peripheral vs. central DEXA scan used for?
- Central: used for larger bones like the spine or hips
- Peripheral: used for screening ONLY: wrist, heel, leg, fingers
Which “T score” on a DEXA scan is considered indicative of osteoporosis?
T score < -2.5
What is the recommended type of calcium supplement for replacing the calcium in someone with hypocalcemia/osteoporosis; what if they have low stomach acid?
- Calcium Carbonate (recommended)
- Calcium citrate if LOW stomach acid
What EKG finding is indicative of hypercalcemia vs. hypocalcemia?
- Hypercalcemia = shortened QT interval –> reflects accelerated repolarization
- Hypocalcemia = prolonged QT interval
What are the actions of 1,25-OH-vit D on the bone, kidney, and gut?
- Bone = ↑ Ca2+ resorption; stimulate osteoclasts
- Kidney = ↑ Ca2+ and PO4 reabsorption
- Gut = ↑ Ca2+ and PO4 absorption
↑ TSH and ↑ T4 would be indicative of what underlying condition?
TSH producing tumor
What are 2 opthalmic findings assoc. w/ hyperthyroidism?
- Lid lag
- Exophthalmos
What is often the only thing needed for the diagnosis of Graves disease?
History and PE
Which lab tests can be useful in supporting diagnosis of Graves disease, but are not needed?
- TSH level (will be suppressed)
- Thyroid scan will show unique homogenous uptake of 131I
- TSI antibody, unique to Graves, but not needed for diagnosis
What will a thyroid scan of someone with Graves show?
Homogenous DIFFUSE ↑ uptake
What are 3 pitfalls to using a thyroid scan for Graves diagnosis?
- Time consuming and expensive
- The isotopecosts more (iodine)
- Scanning at 6 hours and at 24 hours
Which medication is of utmost importance in controlling the cardiovascular and neurological sx’s of Graves?
Beta blockers –> specifically non-selective beta-blockers
If a patient cannot tolerate a beta-blocker, due to asthma, what else can be given for Graves disease?
Trial of CCB
When evaluating a thyroid nodule found on exam, which test is critical to the work up, why?
TSH level –> critical to know if nodule or gland is hyperfunctioning
If someone with a thyroid nodule has low TSH, what is the next step in diagnosing the patient?
- Thyroid scan
- Something is suppressing the TSH
If someone with a thyroid nodule has normal TSH, what is the next step in diagnosis?
- Fine needle aspiration (FNA)
- If TSH is not suppressed, have to see what the nodule is doing; may be cold…. not producing thyroid hormone
B. Toxic nodule
What are some structures in the neck that you should be worried about a benign thyroid nodule potentially damaging?
- Recurrent laryngeal N.
- Parathyroid glands
What are 5 pieces of information which are helpful in predicting that a thyroid nodule is benign?
- Family hx of benign nodules
- Hashimoto’s
- TENDERNESS
- Mobile nodule
- Concomitant diagnosis of hypo- or hyperthyroidism
What are 6 factors which help predict a thyroid nodule may be malignant?
- Very young pt
- Very old pt
- MEN
- Hx of neck irradiation
- FIRM, FIXED nodules
- Lymphadenopathy
Why are we more worried about “cold” thyroid nodules?
- Represent 85% of all thyroid nodules
- 85% of them are benign, BUT 15% are malignant
If a FNA comes back showing a thyroid nodule is benign, what is the next best step in treatment?
- Monitor by US
- Surgery if further growth or suspicious cytology
What are the classic findings of TSH and T4 in a patient with pituitary adenoma as source of hyperthyroidism?
- Very high TSH
- High to very high T4
What is your working diagnosis based off the labs?
Hypothyroid - Hashimoto burn out
What would the seurm levels of TSH, T4, and T3 be like in patient with hypothyroidism due to pituitary failure?
Loss of lateral aspects of eyebrows (Queen Anne Sign) is a finding associated with what endocrine abnormality?
HYPOthyroidism
What cardiovascular findings are typical of hypothyroidism?
- Bradycardia
- ↓ systolic pressure
- ↓ or ↑ diastolic pressure
- Non-pitting edema (myxedema)
- Pitting edema may be seen
What is the most useful lab test in diagnosis hypothyroidism and should be the first test ordered to assess thyroid function?
TSH
Which cause of hypothyroidism could be misleading based on TSH levels?
Pituitary dysfunction –> ↓ TSH (usually would expect ↑ TSH)
With the availability of free T4, why should the measure of total T4 (or total T3) be avoided?
Total T4 and T3 is affected by the binding proteins
Which serum antibody is the most helpful in making the diagnosis of autoimmune hypothyroidism?
Anti-TPO
Thyroid stimulating immunoglobulins (TSI) levels can be useful in the diagnosis of what?
Graves
What is the most important aspect of assessment when using thryoid replacement therapy?
- Clinical observation of the sx’s is most important
- Watch for over treatment
- Development of sub-clinical or overt HYPERthyroidism
