Thyroid/Para Lab Med

Question 1

Purpose of parathyroid hormone plus Ca++

Answer 1

• 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

Question 2

normal PTH and Ca++

Answer 2

• PTH: 15-65

- Ca: 8.6-10.2

Question 3

PTH and Ca++ in primary hyperparathyroidism

Answer 3

• PTH: >65

- Ca: >10.2

Question 4

PTH and Ca++ in secondary hyperparathyroidism

Answer 4

• PTH: >65

- Ca: <10.2

Question 5

PTH and Ca++ in nonparathyroid hypercalcemia

Answer 5

• PTH: <65

- Ca: >10.2

Question 6

PTH and Ca++ in hypoparathyroidism

Answer 6

• PTH: <15

- Ca: <8.6

Question 7

PTH and Ca++ in nonparathyroid hypocalcema

Answer 7

• PTH: 15-65

- Ca: <8.6

Question 8

interpret the results of a phosphorus test ordered in a pt w/ hyperparathyroidism

Answer 8

-low levels of phosphorus in the blood may be d/t or associated w/ hypercalcemia esp. d/y hyperparathyroid

Question 9

interpret the results of a phosphorus test ordered in a pt w/ hypoparathyroidism

Answer 9

-high levels of phosphorus in the blood may be d/t or associated w/ hypoparathyroid

Question 10

what is the purpose of ordering a plasma calcitonin?

Answer 10

• to help diagnose and monitor c-cell hyperplasia and medullary thyroid CA
• to screen those at risk for MEN-2

Question 11

what is the purpose of an alkaline phosphatase?

Answer 11

• 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

Question 12

explain the meaning of an elevated alk phos from bone

Answer 12

possible condition causing increased bone cell activity is present

Question 13

when to order serum magnesium in a pt w/ a parathyroid disorder

Answer 13

-in pts w/ hypocalcemia (PTH enhances tubular reabsorption of magnesium)

Question 14

explain how thyroglobulin can be used to monitor a pt w/ thyroid CA

Answer 14

• 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

Question 15

what is the purpose of monitoring Vit. D tests to evaluate parathyroid disease?

Answer 15

-aid in the diagnosis of primary hyperparathyroidism, hypoparathyroidism, pseudohypoparathyroidism, renal osteodystrophy and vit. D resistant rickets

Question 16

when to order vit. D test in parathyroid disorders

Answer 16

• 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

Question 17

source of 25-hydroxyvitamin D and calcitriol

Answer 17

• the major form found in the blood

- relatively inactive precursor to the active hormone, calcitriol (1,25-dihydroxyvitamin D)

Question 18

ID the cause of elevated calcitriol

Answer 18

• may occur when there is excess PTH

- or when there are diseases: sarcoidosis or some lymphomas (can make calcitriol outside of kidneys)

Question 19

what is the meaning of low TSH result?

Answer 19

• 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

Question 20

what is the meaning of high TSH result?

Answer 20

• 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

Question 21

reference range for TSH

Answer 21

0.45 to 4.5 uUI/mL

Question 22

if a pt is on thyroid hormone replacement, state when the TSH should be drawn

Answer 22

• blood samples should be drawn before the dose is taken

- and to monitor tx

Question 23

given a pts free T4 result, select the correct interpretation of the result

Answer 23

• in general, high free T4 may indicate an overactive thyroid gland
• low free T4 may indicate underactive thyroid
• test results alone are not diagnostic

Question 24

When to order a free T3

Answer 24

• 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

Question 25

when to order thyroid antibodies

Answer 25

• 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

Question 26

what are the thyroid antibodies

Answer 26

• TPO
• TGAb
• TSHRAb - incuding TSI and TBII

Question 27

when to order CEA

Answer 27

• to monitor CA tx including response to therapy and recurrence
• as an indicator of the amount of CA or size of tumor present