Lecture Notes: Metabolic and Endocrine Disorders - Thyroid

Key Thyroid Tests

• TSH (Thyroid Stimulating Hormone):
  • Primary test to diagnose thyroid issues.
  • Highly sensitive; preferred initial test.
• Free T4:
  • Active portion of T4, used to support diagnosis of hypo/hyperthyroidism.
  • More reliable than TSH when thyroid is unstable.
• Total T4:
  • Less reliable; affected by medications and conditions like pregnancy.
• Free T3 and Total T3:
  • Rarely needed; focus on TSH and Free T4.
• Thyroid Peroxidase Antibody (TPO):
  • Used to detect autoimmune thyroid diseases.
• Reverse T3:
  • Biologically inactive, used in specific cases (e.g., sick euthyroid syndrome).

Hyperthyroidism

• Characterized by excessive thyroid hormone production.
• Common Causes:
  • Graves' disease (autoimmune)
  • Subacute thyroiditis
  • Toxic multinodular goiter
  • Inappropriate use of thyroid hormone
  • Pituitary tumor (rare)
• Lab Indicators:
  • Low TSH, high Free T4 in most cases.
  • High TSH and Free T4 indicates pituitary gland issue.
• Symptoms:
  • Weight loss, muscle loss, increased appetite
  • Emotional upsets, memory issues, racing mind
  • Tremors, tachycardia, heat intolerance
  • Irregular menstruation, goiter, GI issues
  • Sweating, thinning hair, velvety skin
  • Eye symptoms: Exophthalmos, lid lag

Physical Examination Findings

• Cardiovascular: Tachycardia, pulse pressure widening
• Skin: Thinning hair, increased pigmentation
• Neurological: Tremors, hyperreflexive deep tendon reflexes
• Eye: Protrusion (exophthalmos), lid lag
• Thyroid gland: Possible nodules or bruit

Long-term Effects of Untreated Hyperthyroidism

• Growth alterations in children
• Osteoporosis, heart disease, mental illness, infertility

Diagnostic Testing

• Initial Tests:
  • TSH (usually < 4.35), Free T4
• Additional Tests:
  • Nuclear scan with radio-labeled iodine
  • Ultrasound, fine needle biopsy for thyroid masses

Differential Diagnosis

• Graves' disease, thyrotoxicosis, thyroid cancer
• Medications and conditions affecting thyroid hormones

Graves' Disease

• Most common cause of hyperthyroidism
• Autoimmune disorder associated with other autoimmune conditions
• Manifestations:
  • Hypermetabolic state, sympathetic overactivity
  • Diffusely enlarged thyroid (goiter)
  • Eye symptoms: Edema, ptosis, diplopia
• Pathophysiology:
  • Presence of antibodies to TSH receptor
  • Low TSH levels, high thyroid hormones

Management of Hyperthyroidism

• Managed by endocrinology
• Treatments:
  • Radioactive iodine (causes thyroid cell destruction)
  • Antithyroid medications (PTU, MMI)
  • Beta blockers for symptom relief
  • Surgery (subtotal or total thyroidectomy)
• Patient Education:
  • Disease process, treatment adherence, lifestyle changes

Thyroid Storm

• Triggers: Infection, medication withdrawal, stress
• Symptoms: Fever, nausea, confusion, tachycardia
• Requires emergency treatment, hospitalization

Subclinical Hyperthyroidism

• Undetectable TSH, normal T4 and T3
• Treatment is controversial, referred to endocrinology