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Lab Modules > Module 4 - Endocrine > Flashcards

Module 4 - Endocrine Flashcards

1
Q

Low blood sugar promotes _____ release

A

glucagon

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2
Q

High blood sugar promotes _____ release

A

insulin

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3
Q

What is the best indicator of glucose homeostasis (regulation of catabolism and anabolism) ?

A

Fasting Plasma Glucose (FPG)

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4
Q

FPG:

measures only at a ____ point in time (does not represent average)!

A

single

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5
Q

FPG:
Patients should be instructed to ____ for at least 8 hours (8-12 is ideal), therefore overnight is most convenient (assay in the morning)

A

FAST

*only water can be consumed (no coffee, juices, gums, etc)

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6
Q

Describe the Random Plasma Glucose test

A
  • Blood is taken at any time during the day regardless of food intake
  • Less valuable than fasting glucose in terms of diagnostic value (variable)
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7
Q

What is the OGTT

A

Oral Glucose Tolerance Test:
-Testing the ability of the pancreas to secrete insulin to manage the glucose load and also the body’s response to the insulin

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8
Q

Describe the OGTT in non-pregnant patients

A
  • Patient fasts (at least 8 hours)
  • Given 75g of glucose (drink in 5 mins)
  • Blood taken 2 hours after glucose given
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9
Q

Describe the OGTT in pregnant patients

A
  • Patient fasts (at least 8 hours)
  • Givne 75g of glucose (drink in 5 mins)
  • Blood taken at both 1 and 2 hours after glucose given
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10
Q

When does gestational diabetes usually show up?

A

at 24-28 weeks

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11
Q

Who is screened for GDM ?

A

Every pregnant patient between 24 and 28 weeks gestation

*if there is a high risk of GDM based on multiple clinical factors, screening should be offered at any stage in the pregnancy

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12
Q

What can increased blood glucose during pregnancy cause?

A
  • Fetal malformations (1st trimester)

- Metabolic complications and macrosomia (large babies) at birth

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13
Q

What is the 1st step in screening for GDM?

A

50 g glucose challenge test with PG 1 hour later

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14
Q

50 g glucose challenge test with PG 1 hour later:

If the result is <7.8 mmol/L what does that mean?

A

Normal value

Reassess at 24-28 weeks if tested earlier

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15
Q

50 g glucose challenge test with PG 1 hour later:

If the result is 7.8-11.0 mmol/L what does that mean?

A

Perform a 75 g OGTT and measure FPG, 1hPG, and 2hPG

FPG > 5.3
1hPG > 10.6
2hPG > 9.0

If 1 value is met or exceeded

It means they have GDM

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16
Q

50 g glucose challenge test with PG 1 hour later:

If the result is >11.0 mmol/L what does that mean?

A

Means they have GDM

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17
Q

Describe the Glycosylated or Glycated Hemoglobin (Hgb A1C)

A
  • Glucose is irreversibly bound to hemoglobin in proportion to the average blood glucose
  • Lifespan of RBCs = 120 days therefore A1C reflects glucose over the last 2-3 months
  • Patients with persistently high glucose can have A1C’s as high as 20%
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18
Q

What can cause an A1C to be falsely high?

A
  • Uremia
  • Alcoholism
  • Increased TGs
  • Splenectomy
  • Pregnancy
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19
Q

What can cause an A1C to be falsely low?

A
  • Hemolysis

- Pregnancy

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20
Q

What lab value indicates diabetes for FPG?

A

> 7 mmol/L

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21
Q

What lab value indicates diabetes for random plasma glucose?

A

> 11.1 mmol/L

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22
Q

What lab value indicates diabetes for a 2h OGTT ?

A

> 11.1 mmol/L

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23
Q

What lab value indicates diabetes for A1C ?

A

> 6.5%

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24
Q

What medications cause hyperglycemia ?

  • these lead to reduced insulin and therefore increased blood sugar
  • see slide 13 for the MOA
A

Diuretics:

  • Thiazides
  • Loop diuretics
  • Metalozone

Atypical antipsychotics:

  • Olanzapine
  • Clozapine

Beta-blockers:
-Metoprolol

Steroids/hormones:

  • Glucocorticoids
  • Oral contraceptives & estrogens
  • Thyroid hormones

HIV therapies:

  • Protease inhibitors (“navirs”)
  • NRTIs (ex. tenofovir)
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25
Q

What is the 1st intervention for pre-diabetic patients?

A

diet and exericise

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26
Q

When do you re-test for pre-diabetic patients?

A

annually

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27
Q

Describe how thyroid hormones work (negative feedback loop)

A
  • Hypothalamus in brain releases TRH (thyrotropin releasing hormone)
  • Anterior pituitary releases TSH (thyroid stimulating hormone)
  • Thyroid gland releases T4 (thyroxine) and T3 (triiodothyronine)

*these hormones prevent the release of TRH and therefore TSH

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28
Q

How does cold affect TRH?

A

increases the amount of TRH, TSH and T3 and T4 to increase metabolic rate to compensate for the cold

29
Q

How does stress affect TSH?

A

stress produces cortisol which decreases the amount of TSH and therefore the amount of thyroid hormones is decreased and hypothyroidism may develop

30
Q

What is TSH ?

A

-A glycoprotein with an alpha and beta subunit similar to other hormones secreted by the anterior pituitary (LH and FSH)

31
Q

Patients with primary hypothyroidism and major symptoms usually have elevations in TSH > ____ mU/L (mild symptoms 10-20 mU/L)

A

20

32
Q

TSH may be falsely ____ in pregnancy

A

high

33
Q

Why may TSH be falsely high in pregnancy?

A

because TSH and HCG are structurally similar

34
Q

TSH reflects what?

A

long-term thyroid status (whereas T4 reflects short term)

35
Q

TSH is ordered ______ before other thyroid tests

A

FIRST

36
Q

Thyroxine is _____ T4

A

free

37
Q

Thyroxine (Free T4):

Secreted by the _____ gland

A

thyroid

38
Q

Thyroxine (Free T4):

How much T4 is normally produced daily by adults?

A

80 mcg

39
Q

Thyroxine (Free T4):

____ half life than T3 (7 days) but ____ potent

A

Longer half life

Less potent

40
Q

Thyroxine (T4):

Why must you read the lab report carefully?

A

T4 can be reported as total or free (total T4 measures both bound and free T4)

41
Q

When is Thyroxine (Free T4) ordered?

A

if patient has signs and symptoms of hypothyroidism and TSH is normal or near normal

42
Q

Triiodothyronine (Free T3):

___% secreted by thyroid gland, remainder formed by deiodination of T4 by liver and kidneys

A

25

43
Q

Triiodothyronine (Free T3):

How much of T3 is normally produced daily by adults

A

30 mcg

44
Q

Triiodothyronine (Free T3):

___x more potent than T4, but has a _____ half life (1 day)

A

3-4x more potent

shorter half life

45
Q

Triiodothyronine (Free T3):

Is it usually ordered?

A

Not usually ordered; only if hyperthyroidism is suspected, TSH is low and T4 is normal (T3 toxicosis)

46
Q

List signs and symptoms of HYPOthyroidism

A
  • lethargy/depression
  • constipation
  • weight gain
  • dry skin, hair and brittle nails
  • cold intolerance
  • paresthesias
  • slow deep tendon reflexes
  • decreased sweating
  • memory impairment
  • facial puffiness
  • slow motor activity
47
Q

List signs and symptoms of HYPERthyroidism

A
  • nervousness
  • fatigue
  • weight loss
  • heat intolerance
  • increased sweating
  • tachycardia
  • muscle atrophy
  • exophthalmos (bulging eyes)
48
Q

Which drugs decrease thyroid hormones (T3 and T4)

A
  • glucocorticoids
  • amiodarone
  • 6-MP
  • sulfonamides
  • lithium
  • phenobarb
  • antacids and binders
49
Q

Which drugs increase thyroid hormones (T3 and T4)

A
  • amphetamines
  • amiodarone
  • high dose propranolol
  • metoclopramide
  • high dose salicylates
50
Q

What lab values will indicate sub-clinical HYPOthyroidism?

A
  • Slight increase in TSH
  • Normal Free T4
  • Normal Free T3
51
Q

What is the explanation for sub-clinical HYPOthyroidism?

A

May occur in elderly patients, postpartum, inadequate replacement therapy etc.

May or may not treat depending on symptoms and labs

52
Q

What lab values will indicate primary HYPOthyroidism?

A
  • High TSH
  • Low Free T4
  • Low Free T3
53
Q

What is the explanation for primary HYPOthyroidism?

A

Problem at the THYROID.

Thyroid is being stimulated but can’t produce hormoens

54
Q

What lab values will indicate central HYPOthyroidism?

A
  • Normal or low TSH
  • Normal or low Free T4
  • Normal or low Free T3
55
Q

What is the explanation for central HYPOthyroidism?

A

Feedback mechanisms to pituitary or hypothalamus not working properly

56
Q

What lab values will indicate HYPERthyroidism?

A
  • Low TSH
  • High Free T4
  • High Free T3
57
Q

What is the explanation for HYPERthyroidism?

A

Graves’s disease (60-90%) of cases - autoimmune disease activating the TSH receptor producing T3 and T4

58
Q

How often should we monitor TSH and Free T4 after initiating therapy or changing dose?

A

-Reassess every 6-8 weeks after initiating therapy or changing dose (Css of TSH = about 6 weeks)

59
Q

If patient on stable dose, how often should we monitor TSH and Free T4?

A

annually

60
Q

If newly treated, symptoms such as fatigue, fast HR and puffiness tart to improve within _____ weeks, but anemia, skin/hair changes may take ______ to resolve

A

2-3 weeks

months

61
Q

If a hypothyroid patient becomes pregnant, monitor TSH and Free T4 every _____

A

trimester

62
Q

If a hypothyroid patient becomes pregnant, their requirements ______

A

increase (up to 50% greater hormone requirements in pregnancy)

63
Q

If a hypothyroid patient becomes pregnant and requires a dose increase, what dose increase do we recommend?

A

increase by 2 tablets of current dose per week

64
Q

What is the TSH target range for first trimester (week 1-12)?

A

0.1-2.5 mU/L

65
Q

What is the TSH target range for second trimester (week 13-26)?

A

0.2-0.3 mU/L

66
Q

What is the TSH target range for third trimester (week 27 - end of pregnancy)?

A

0.3-3.0 mU/L

67
Q

How do we manage hypothyroid patients after giving birth (post-partum) ?

A
  • Reduce dose back to pre-conception dose

- Assess TSH levels 6-8 weeks postpartum for any dose adjustments

68
Q

If someone has TSH that is 19.8 and Free T4 that is 6.2, what thyroid abnormality do they have and how do you know?

What medication will they be started on?

A

primary HYPOthyroidism

-TSH is high (stimulated thyroid) but thyroid is not producing enough hormones (T4 is low) - thyroid problem

started on levothyroxine

Lab Modules (7 decks)

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