Hypo & Hyperthyroidism Flashcards
Thyroid Function Tests
- TSH is used to screen for hypo and hyperthyroidism.
- Free T3 and T4 can confirm diagnosis
- Thyroid scan can be used to evaluate for goiter
- Routine screening is not recommended
- Screen women before pregnancy and in first trimester
Hyperthyroidism
Excessive levels of thyroid hormone
- May be life-threatening
- Caused by Grave’s Disease, anterior pituitary disorders, Plummer’s disease, amiodarone therapy
- Commonly Causes Grave’s Disease
Clinical effects from hypermetabolic state
- Heat intolerance, tachycardia
Treatment: anti-thyroid drugs
- Propylthiouracil (PTU) and methimazole
Anti-Thyroid Agents: Pharmacodynamics
PTU, methimazole (Tapazole)
- Block synthesis of thyroxine and triiodothyronine
- Neither drug treats the underlying pathology in hyperthyroidism
- High relapse rates; studies show less if treated for 18-24 months
Goal of Treatment: correcting hypermetabolic state
Hyperthyroidism: Drug Therapy
Antithyroid drugs used for remission:
- Beta blockers may be used to reduce symptoms while waiting for antithyroid drugs to work
- Iodides (potassium iodide or Lugol’s solution) may be used as adjuvant treatment
Antithyroid drugs are used for at least a year in treating Grave’s disease
Older patients may respond best to radioactive iodine
Pregnant patients are treated with PTU because it is a bit safer
Anti-thyroid Agents: Precautions, Contraindications, ADRs, and Drug Interaction
- Precautions & Contraindications
- – Pregnancy category D: readily crosses the placenta; recommendation NOT to get pregnant while on these drugs
- – PTU not recommended in children
- ADRs: agranulocytosis, drowsiness, HA, alopecia, skin rashes, renal/hepatic failure
- Drug Interaction: lithium, warfarin
Hyperthyroidism- Drug Therapy: Preoperative drugs to avoid Thyroid Storm while awaiting thyroid surgery
- Antithyroid drugs
- Beta blockers
- Potassium iodide
Hyperthyroidism- Drug Therapy: Monitoring and Outcome Evaluation
Monitoring - Clinical status - Thyroid function tests: TSH and free T4 - Assessment of visual acuity Outcome evaluation - Based on TSH and free T4 levels - Referral to endocrinology as necessary
Hyperthyroidism- Drug Therapy: Patient Education
- Overall treatment plan
- Length of treatment
- Medication Administration
- Precautions if treated with idone-131 (I133)
Hypothyroidism: Primary and Secondary
Primary
- Congenital hypothyroidism
- Hashimoto’s Thyroiditis: an immune-mediated disorder where TSH receptors are damaged
- Subacute thyroiditis: inflammation of thyroid
Secondary
- Pituitary or hypothalamic failure
- Cushing’s Syndrome
- Overtreatment with antithyroid drugs
Hypothyroidism: Goals of Treatment & Rational Drug Selection
Goals of Treatment
- Correction of hypometabolic state and return to euthyroid state
Rational Drug Selection
- Synthetic thyroid hormone
- Generic vs. brand name controversy
Thyroid Hormones: Pharmacodynamics
- T3, T4, and liotrix (a 4:1 mixture of T3 and T4)
- These hormones produce the same effects in the body as do endogenous thyroid hormones
- They also produce a negative feedback loop to reduce further secretion of TSH and thyroid hormones
- T4 is the drug of choice for thyroid replacement and suppression therapy because of its longer half-life
Hypothyroidism: In Pregnancy and Children
Pregnancy
- Untreated hypothyroidism increases maternal health risks, still births, low birth weight, and possible abnormal fetal brain development
- T4 is pregnancy category A
Infants and children with hypothyroidism need treatment for normal cognitive and physical development
Hypothyroidism: Associated Diseases
Recent acute MI
CAD
Osteoporosis: women with osteoporosis require careful monitoring
Infertility and menstrual irregularity: may improve with thyroid hormone replacement
Depression: hypothyroid evaluation should be part of depression workup
Hypothyroidism: Monitoring
- TSH and free T4 levels should be evaluated:
- – every 4-8 weeks until euthyroid state reached
- – during pregnancy, at 8 weeks and 6 months gestation
- Clinical symptoms frequently do not parallel actual value
- Evaluate for anemia
- Monitor BP and lipids
Hypothyroidism: Outcome Evaluation
- Reduction of clinical symptoms and normal TSH/Free T4
- Endocrine consult considered for:
- – Pediatric patients
- – Pregnant patients
- – Cardiac patients
- – Complex patients or those not responding to therapy
