Endocrine Labs Flashcards
Signs & Symptoms of Hypothyroidism
fatigue or sluggishness weight gain cold intolerance dry skin, brittle hair constipation, slows digestion slows heart and respiration menstrual irregularities
Signs & Symptoms of Hyperthyroidism
anxiety, irritable, difficulty sleeping weakness in arms and legs tremors feels hot, perspires a lot weight loss frequent bowel movements irregular heartbeat
Can you order a TSH if the patient presents with one symptom alone?
Yes
Name the 5 thyroid function tests
TSH Total T4 Total T3 Free T4 Free T3
Secretion of T4 and T3 by the thyroid gland is regulated by TSH from the?
pituitary
TSH levels are controlled through…
a negative feedback system
Describe the negative feedback system of TSH
Starts with an abnormal serum T4 or T3 level, which triggers thyrotropin-releasing hormone (TRH) in the hypothalamus to trigger the release of TSH
What is the normal value range for TSH?
0.4-4.2 mU/L for adults
What is the best test to assess thyroid function?
TSH
If TSH is normal, does this allow for further testing?
No
An elevated TSH points to?
Hypothyroidism
A low TSH points to?
Hyperthyroidism
An elevated TSH can be followed with what test?
Free T4 (to determine the degree of hypothyroidism)
A low TSH can be followed with what test?
Free T4 and possibly a Free T3 (to determine the degree of hyperthyroidism)
What test is used to monitor therapy in patients with hypothyroidism?
TSH test
Individuals with hypothyroidism take what thyroid medication?
levothyroxine
If a patient taking levothyroxine has a high TSH, they are still in the “hypo” range and need to do what to their medication dose?
increase it
If a patient taking levothyroxine has a low TSH, they are still in the “hyper” range and need to do what to their medication dose?
Reduce it
After administering levothyroxine to a patient when should they come back in for a check-up?
4-6 weeks to monitor TSH levels
What could be reasons for an abnormally elevated TSH level?
Primary hypothyroidism
Medication interactions
Certain tumors
What could be reasons for an abnormally low TSH level?
Primary hyperthyroidism
Euthyroid sick disease
Thyroid nodules or goiter
These labs measure both the amount of T4 or T3 that is bound to proteins in the blood and what is not bound
Total T4 and Total T3
These labs are not commonly used in primary care
Total T4 and Total T3
These labs increase in hyperthyroidism and decrease in hypothyroidism
Total T4 and Total T3
These labs measure only the amount of T4 or T3 that is not bound to protein and is therefore immediately available for cellular utilization
Free T4 and Free T3
What test can be ordered to confirm TSH results?
Free T4
This test should be elevated in hyperthyroidism and decreased in hypothyroidism?
Free T4
What test may be used in confirming hyperthyroidism?
Free T3 (in addition to Free T4)
These tests are used routinely to monitor therapy?
TSH, Free T4, and Free T3
If a TSH level is below normal range, what do you think of? And what should you order to confirm it?
Think of Hyperthyroidism
Order FT4 and FT3 to confirm
What should you do if someone has hyperthyroidism?
Refer!
If a TSH level is above normal range, what do you think of? And what should you order to confirm it?
Think of hypothyroidism
Order FT4 to confirm
High TSH and low FT4 confirms hypothyroidism what should you do next?
Start levothyroxine. Monitor with periodic TSH.
High TSH and normal FT4, this is considered?
“subclinical hypothyroidism”
What type of cases of “subclinical hypothyroidism” should be treated?
Treat if symptomatic or TSH>10 or planning pregnancy
High TSH and high FT4, what does this require?
Referral
If labs don’t make sense (such as high TSH and high FT3, or low TSH and low FT4), the problem may be what instead? What do you do?
Pituitary and refer
What lab tests can be used to diagnose or to screen for DM?
Fasting blood glucose level (FBG)
Glycosylated hemoglobin (HbA1C)
Oral glucose tolerance test (OGTT)
What are the symptoms of DM?
polyuria, polydipsia, weight loss, fatigue
What an be used for a patient with symptoms of DM that is used for diagnostic purposes, but not for screening?
Random blood glucose level > or equal to 200mg/dL
What percent of patients with DM have type 1? type 2?
5% with Type 1 DM
95% with Type 2 DM
Is screening recommended for DM type 1?
No
If a screening test returns with a positive result what do you do?
Repeat the same test for confirmation
The DM tests have good what _____, but poor _______?
good specificity
poor sensitivity
If a patient has HTN what else do you screen for?
DM
What should the patient do before a fasting blood glucose (FBG)?
Fast for 8 hours
Can the “glucose” in the CMP be utilized for a FBG?
Yes, as long as the patient has been fasting for 8 hours.
A FBG level of greater than or equal to 126 mg/dL on two separate tests confirms?
DM
What is the normal value for FBG?
<100 mg/dL
A value of ______ on a FBG means the patient could have impaired glucose tolerance, and is at risk for DM
100-126 mg/dL
Does the HbA1C require fasting?
No
What does the A1C reflect?
average blood sugar levels for the 3 month period before he test
An A1C of _____ on 2 separate tests, confirms the diagnosis of DM
> 6.5%
Values between _______ are at high risk for developing DM
6.0-6.4%
Values between _______ are considered normal
5.0-6.0%
What could affect the results of HbA1C?
changes to RBCs (e.g., anemia, chronic blood loss, toxicities, renal failure, pregnancy, sickle cell anemia)
This test is considered “first-line” for diagnostic purposes, but is not highly recommended for screening purposes
oral glucose tolerance test (OGTT)
What other non-laboratory exams should a patient with DM have done?
eye, foot, and dental exams
monitoring of BP, weight, diet, exercise, and smoking cessation
Laboratory exams used to monitor patients with DM include:
testing urine for albumin (annually)
lipid panel (annually)
monitor liver function and renal function through the CMP (annually)
A1C to monitor glycemic control (biannually in stable patients, quarterly in unstable patients)
What is the goal for A1C?
A1C <7%
