Thyroid/Para Lab Med Flashcards
Purpose of parathyroid hormone plus Ca++
- diagnosis of parathyroid dz and other dz of Ca homeostasis
- monitoring patients undergoing renal dialysis
- PTH measurement is very useful in the ddx and management of hypercalcemia
normal PTH and Ca++
- PTH: 15-65
- Ca: 8.6-10.2
PTH and Ca++ in primary hyperparathyroidism
- PTH: >65
- Ca: >10.2
PTH and Ca++ in secondary hyperparathyroidism
- PTH: >65
- Ca: <10.2
PTH and Ca++ in nonparathyroid hypercalcemia
- PTH: <65
- Ca: >10.2
PTH and Ca++ in hypoparathyroidism
- PTH: <15
- Ca: <8.6
PTH and Ca++ in nonparathyroid hypocalcema
- PTH: 15-65
- Ca: <8.6
interpret the results of a phosphorus test ordered in a pt w/ hyperparathyroidism
-low levels of phosphorus in the blood may be d/t or associated w/ hypercalcemia esp. d/y hyperparathyroid
interpret the results of a phosphorus test ordered in a pt w/ hypoparathyroidism
-high levels of phosphorus in the blood may be d/t or associated w/ hypoparathyroid
what is the purpose of ordering a plasma calcitonin?
- to help diagnose and monitor c-cell hyperplasia and medullary thyroid CA
- to screen those at risk for MEN-2
what is the purpose of an alkaline phosphatase?
- to determine causes of high and low alk phos
- to help detect liver and bone dz
- an ALP isoenzyme can help determine the source - liver or bone
- sx that suggest a bone disorder are bone pain, increased frequency of fractures, and deformed bones
explain the meaning of an elevated alk phos from bone
possible condition causing increased bone cell activity is present
when to order serum magnesium in a pt w/ a parathyroid disorder
-in pts w/ hypocalcemia (PTH enhances tubular reabsorption of magnesium)
explain how thyroglobulin can be used to monitor a pt w/ thyroid CA
- it can be used as a tumor marker to evaluate the effectiveness of tx for thyroid CA and to monitor for recurrence
- the most common types of thyroid CA frequently produce thyroglobulin resulting in increased levels in the blood
- it can be used along w/ TSH before thyroid CA tx to determine if the CA produces it or not
what is the purpose of monitoring Vit. D tests to evaluate parathyroid disease?
-aid in the diagnosis of primary hyperparathyroidism, hypoparathyroidism, pseudohypoparathyroidism, renal osteodystrophy and vit. D resistant rickets
when to order vit. D test in parathyroid disorders
- determine if bone weakness, malformation or abnormal metabolism of Ca is occurring as a result of a deficiency or excess of vit. D
- help diagnose or monitor problems w/ parathyroid gland functioning since PTH is essential for vit. D activation
source of 25-hydroxyvitamin D and calcitriol
- the major form found in the blood
- relatively inactive precursor to the active hormone, calcitriol (1,25-dihydroxyvitamin D)
ID the cause of elevated calcitriol
- may occur when there is excess PTH
- or when there are diseases: sarcoidosis or some lymphomas (can make calcitriol outside of kidneys)
what is the meaning of low TSH result?
- if the thyroid releases inappropriately large amounts of T3 and T4, the pt may experience sx associated w/ hyperthyroidism
- the pts immune system produces antibodies that act like TSH, leading to the production of excessive amounts of thyroid hormone
- in response, the pituitary may produce less TSH - usually leading to low levels in the blood
what is the meaning of high TSH result?
- if there is decreased production of thyroid hormones by the thyroid, the pt may experience hypothyroid sx
- the immune response causes inflammation and damage to the thyroid so it produces low levels of thyroid hormone
- in response, the pituitary may produce more TSH resulting in high levels in the blood
reference range for TSH
0.45 to 4.5 uUI/mL
if a pt is on thyroid hormone replacement, state when the TSH should be drawn
- blood samples should be drawn before the dose is taken
- and to monitor tx
given a pts free T4 result, select the correct interpretation of the result
- in general, high free T4 may indicate an overactive thyroid gland
- low free T4 may indicate underactive thyroid
- test results alone are not diagnostic
When to order a free T3
- when someone has abnl TSH
- as part of the investigative w/u when a pt has sx suggesting hyperthyroidism, esp if T4 is not elevated
when to order thyroid antibodies
- when a pts has abnl TSH and/or free T4 or s/s of low or high level of thyroid hormones
- presence of goiter, esp. if the cause is suspected to be autoimmune
what are the thyroid antibodies
- TPO
- TGAb
- TSHRAb - incuding TSI and TBII
when to order CEA
- to monitor CA tx including response to therapy and recurrence
- as an indicator of the amount of CA or size of tumor present
