Endocrine disorders Flashcards
Diagnostic Criteria Lab values for Diabetes
FBG, hgbA1c%, Random plasma glucose
FBG: ≥ 126 (Fasting = no intake for 8hrs other than black coffee or water)
HgbA1c %: ≥ 6.5%
Oral Glucose Tolerance Test
Random Plasma Glucose: ≥ 200 W/ SYMPTOMS
Which is the most accurate and best test for diabetes?
Do you repeat lab testing?
Lab based HgbA1c %
YES
HgbA1c
- Avg amount of glucose in blood over the last 3 months
- More heavily weighted in the last 6 to 8 weeks
- No need to fast
What can effect HgbA1c%? (3)
With less RBCs → lowers A1c % b/c there’s not much RBCs for glucose to hang onto
Recent Blood transfusions/erythropoetin therapy
Chronic renal disease
Oral Glucose Tolerance Test (procedure and purpose)
- Best Dx gestational DM in pregnancy
- Person fasts for 8-16 hours
- FPG checked
- Done at 24-28 weeks for screening
- Give 75gm then tested again in 2hrs
- Fasting: ≥ 92
- One hour: ≥ 180
- Two hour: ≥ 153
Type 1 DM
- Loss of all beta cell function in pancreas
- Dependent on exogenous insulin
- NO PO INSULIN
- S/s: young, thin pt w/DM s/s
Type 2 DM
- Multifactorial, often relate to insulin resistance
- Responds to oral meds → eventually exogenous insulin
- S/s: later in life, obese
Type 1 DM vs. Type 2 DM if can’t tell?
What would you test for?
- Test for autoantibodies
- DM1: Thin pt w/poor response to initial therapy w/metformin of Sulfonylureas
- DM1: Personal of FMHx of autoimmune disease
- Overweight or obese children or adolescents presenting w/apparent DM2 BUT have early presentation of DM1
DM Autoantibodies (4)
- Both Islet cell Abs and GAD65 enzyme released and elevated when pancreatic cells start being destroyed
- Insulinoma associated autoantibodies (low insulin production)
- Insulin antibodies - attack body’s insulin (not commonly detected in adults)
Regulation of Thyroid Hormone production
Hypothalamus → TRH → AP → TSH → thyroid gland → T4
Thyroid Stimulating Hormone
Increased vs. decreased
Presence of thyroid hormone that turns ON/OFF TSH
Elevated = hypothyroid
Decreased = hyperthyroid
INVERSE RELATIONSHIP
Free Thyroxine (FT4)
When would you get this lab?
- Controls feedback system
- Add this on if TSH abnormal → tells you how well thyroid is functioning → monitoring
- Add if TSH normal BUT showing hyperthyroid s/s
Triiodothyronine (T3)
- Converted from T4 by removal of iodine molecule in liver and tissues
- More active form of thyroid hormone
- Useful in evaluation of hyperthyroid - low TSH but normal FT4 then check T3
- If TSH decreased but T4 normal → order T3 to create better dx picture
What do you order for s/s of thyroid disease?
TSH
What do you order to monitor effectiveness of thyroid replacement?
TSH
Thyroid labs to order for initial monitoring of hyperthyroidism
TSH, T4, T3
Once steady → TSH
Serum TSH level Normal, you order…
NO TEST NEEDED
Serum TSH HIGH, you order…
Free T4 added to determine degree of hypothyroidism
Serum TSH LOW, you order…
Free T4 and T3 added to determine degree of hyperthyroidism
-The TSH might be sub normal for weeks. Use T4, sometimes T3.
Thyroid Autoantibodies
What do they do to the thyroid?
- Develop when immune system targets thyroid gland/thyroid proteins resulting in thyroid inflammation and/or disruption of function
- Can result in hyperthyroidism (Grave’s) or hypothyroidism (hasimoto’s)
Two tests for thyroid antibodies and what do they test?
- Thyroid peroxidase (TPO): predicts likelihood that subclinical hypothyroidism will progress to overt hypothyroidism
- Subclinical hypothyroidism → TSH abnormal
- HIGH TSH but NORMAL T3, T4
- Subclinical hypothyroidism → TSH abnormal
- Thyroiglobulin (Tg): Not routinely used except for in those s/p thyroidectomy for thyroid cancer
Best imaging modality for thyroid nodule
What lab would you check as well?
Thyroid ultrasound → suspected thyroid nodule or goiter on exam → NOT DX OR SCREENING TOOL
Check TSH
Malignant Thyroid nodule characteristics on U/S
A.B.H.I.I.M.
- Hypoechoic = more dense
- Microcalcifications
- Border irregularity
- Infiltrative margins
- Abnormal cervical lymph nodes
- Increased intra-nodular vascularity
Nuclear thyroid testing and procedure
- Use radioactive iodine as thyroid will take up iodine → needed to make thyroid hormones for thyroid function
- Procedure
- RI-123 administered either PO or IV
- Just thyroid scan - IV
- Both scan and RAIU → PO ~24rhs prior to scan
- Gamma camera or probe used to check for uptake
- RI-123 administered either PO or IV
- CONTRAINDICATED W/PREGOS
- Avoid certain foods containing iodine (shellfish) and/or meds prior to exam
2 types of radioactive iodine
- I-123 - harmless to thyroid cells
- I-131 - destroys thyroid cells
Thyroid Scan
Used to determine size, shape, and position of thyroid → used for further eval of thyroid nodules
Radioactive Iodine Uptake Scan (RAIU)
- Evaluates function of gland
- Primarily used to determine cause of HYPERthyroidism
Prolactin
- Hormone produced by anterior pituitary - promotes lactation
When is prolactin elevated?
- Normally elevated in pregnant/lactating women
- Cases of a prolactinoma - pituitary tumor which secretes prolactin, typically benign
- Medications: antipsychotics, metoclopramide, verapamil, methyldopamide, verapamil, methyldopa
Result of prolactinoma
Amenorrhea - common result
Imaging for prolactinoma
Brain MRI
Symptoms of prolactinoma
- Headaches
- Visual changes
- Unexplained nipple discharge
Indications for testing prolactin levels
- Symptoms of prolactinoma
- Infertility, a/oligomenorrhea
- In men: decreased libido, low testosterone, infertility, nipple discharge
