Endocrine Diagnostics - Skills

Diabetes Mellitus

• Regulation of blood glucose:
  • Glucose serves as fuel for cellular functions
  • Absorbed in the GI tract and metabolized into glucose from carbohydrates
  • Stored in liver as glycogen
  • Pancreas produces, stores, and releases insulin to facilitate glucose move into cells and out of bloodstream when plasma glucose is high
  • Pancreas produces, stores, and releases glucagon to facilitate glucose breakdown and export into plasma when plasma glucose is low

Types of Diabetes Mellitus

• Type 1:
  • Lack of endogenous insulin
  • Abrupt onset, usually in children
  • Prone to ketoacidosis due to metabolism of fatty acids
  • Treatment focused on glycemic control with diet and exogenous insulin
• Type 2:
  • Endogenous insulin present but problem with insulin utilization or release
  • Usually diagnosed at older age (>40yo)
  • Associated with obesity and dyslipidemia
  • Not prone to ketoacidosis due to insulin presence
  • Treatment focused on glycemic control with diet, exercise, weight loss, etc.

Laboratory Tests for Diabetes Mellitus

• Plasma Glucose:
  • Fasting (normal 70-99 mg/dL)
  • Random (normal 70-140 mg/dL)
  • Finger stick for screening or self-monitoring
  • Used for diagnosis and monitoring of DM Type 2
• Hemoglobin A1C:
  • Venipuncture blood draw
  • Checks average blood sugar over the last 3 months
  • Gold standard for evaluation and management of Diabetes
• C-Peptide:
  • Protein byproduct of pancreas making insulin
  • Measures amount of c-peptide in blood or urine
  • Used in evaluation and management of Type 1 DM
• Oral Glucose Tolerance Test (OGT T):
  • Measures body's ability to process large amount of sugar
  • Must fast for at least 8hrs before test
  • Result is glucose level at the end of the test
  • Used for screening and diagnosis of Type 2 DM
• Urinalysis:
  • Screening test for ambiguous symptoms
  • Used to diagnose or monitor patients with DM
  • Looks for protein, ketones, and glucose
• Liver Function Tests:
  • Follows liver function as a measure of diabetes progression
  • Concerns include high insulin levels causing hepatocyte injury and development of fatty liver leading to increased insulin resistance
• Renal Function Tests:
  • Follows renal function as a measure of diabetes progression
  • Concerns include nephropathy and potential kidney damage

Diabetic Ketoacidosis (DKA) vs. Hyperosmolar Hyperglycemic State (HHS)

• Diabetic Ketoacidosis (DKA):
  • Type 1 DM
  • Precipitated by infection
  • More severe illness
  • Ketoacidosis
  • Short prodromal symptoms (polyuria/polydipsia, N/V, drowsiness)
  • Mortality 5-10%
• Hyperosmolar Hyperglycemic State (HHS):
  • Type 2 DM
  • More common
  • Uncommon
  • Longer prodromal symptoms (days to weeks of weakness, polyuria/polydipsia, poor fluid intake)
  • Mortality 40-60%

Laboratory Tests for DKA vs. HHS

• DKA:
  • Labs to get: BMP, blood glucose, UA for ketones (if positive then serum ketone), arterial blood gas
  • Findings: hyperglycemia, positive ketones in urine and blood, blood pH < 3.10, no acidosis, anion gap, elevated BUN and Cr
• HHS:
  • Labs to get: BMP, blood glucose, UA for ketones (if positive then serum ketone), arterial blood gas
  • Findings: hyperglycemia, no acidosis, anion gap, elevated BUN and Cr

Thyroid Disorders

• Thyroid Function Tests:
  • Purpose: measure concentration of hormones going to/secreted by the thyroid
  • Screen for thyroid/pituitary/hypothalamus
  • Continual assessment of thyroid disorder treatment
  • Detecting antibodies to thyroid tissue
• TSH:
  • Released from anterior pituitary gland as part of a negative feedback loop from T4/T3
  • Causes thyroid to release mostly T4 and some T3
  • Uses: screening for thyroid disease and assessing thyroid function while on treatment
• FT4:
  • Measures the unbound serum T4
  • Uses: in combination with TSH, used to screen for hypo/hyperthyroidism
  • Monitoring disease progression and medical treatment for thyroid conditions
• Thyroid Antibody Labs:
  • Thyroglobulin (Tg) Antibody
  • Thyroid Peroxidase (TPO) antibody: positive in Hashimoto's thyroiditis
  • Thyrotropin Receptor Antibody's (TrAb): Thyroid stimulating immunoglobulin (TSI) - Grave's Disease

Parathyroid Disorders

• Parathyroid Hormone (PTH):
  • Regulates calcium and phosphate levels
  • Produced by parathyroid glands
• Things to Check:
  • Calcium: normal range 8.5-10.2mg/dL
  • First, verify abnormal calcium
  • Total calcium corrected for albumin
  • PTH
  • Vitamin D
  • Phosphorus
  • Corrected calcium = serum calcium + (0.8 x [4.0 - serum albumin])
• Pattern to Check:
  • Start with corrected calcium
  • If abnormal (high or low), then check PTH
  • Correlate calcium level (high or low) with PTH level (high or low)
  • Differentiate primary, secondary, and tertiary with other labs/PMH
  • Vit D, Magnesium, etc.
• Example Pattern:
  • Hyperparathyroidism:
    • Primary (problem with the gland itself)
      • PTH elevated
      • Calcium elevated
      • Vit D normal/elevated
      • Phosphorus normal/low
  • Secondary (problem with end organ, aka bone or kidneys)
    • PTH elevated
    • Calcium low/normal
  • Tertiary (chronic stimulation leading to overproduction of PTH)
    • PTH elevated
    • Calcium low/normal

Adrenal Disorders

• Cortisol insufficiency:
  • Low cortisol
  • Labs: morning blood cortisol level
  • Addison's disease