Drug Therapy for Hyperthyroidism & Hypothyroidism

Thyroid Gland

• is responsible for the secretion of three hormones essential for proper regulation of metabolism.​

  • Thyroxine (T4)​

  • Triiodothyronine (T3)​

  • Calcitonin ​

• Production of T3 and T4 depends on iodine and tyrosine​

• Contain molecules of iodine​

• After released, combine with intracellular proteins- released slowly

Hyperthyroidism Causes

• Graves disease

• Nodular thyroid goiter - enlargement of the thyroid gland

• Thyroiditis - inflammation of the thyroid gland

• Over treatment for hypothyroidism

Hyperthyroidism tx

• Return to a euthyroid state

• Reduce hormone production to relieve symptoms; avoid destruction of the gland​

• * Propylthiouracil is prototype

Hyperthyroidism Clinical Manifestations

• CNS:

  • Nervousness, emotional instability, hyperactive reflexes, insomnia

• CV:

  • Increased blood pressure, cardiac dysrhythmias, high output heart failure

• Respiratory:

  • Shortness of breath, crackles

• GI:

  • Increased appetite, diarrhea, weight loss

• Eyes:

  • Dryness, pain, exophthalmos

Treatment: Propylthiouracil (PTU) MOA

Inhibits production of thyroid hormones & conversion of T4 to T3

Treatment: Propylthiouracil (PTU) Pharmacokinetics

Liver, well absorbed, given Q 8 hrs

Treatment: Propylthiouracil (PTU) Indications

Hyperthyroidism, preop for thyroidectomy

Treatment: Propylthiouracil (PTU) special ages

• Not recommended in children

• Not preferred in older adults

Treatment: Propylthiouracil (PTU) BBW

Liver injury

Treatment: Propylthiouracil (PTU) adverse effects

• Hypothyroid symptoms

• Leukopenia, agranulocytosis

• Rash, alopecia

• CNS: headaches, dizziness

• GI: NV, cholestatic hepatitis

Treatment: Propylthiouracil (PTU) drug-drug

↑effects of anticoagulants

Radioactive Iodine-131 (131I)

• Radioactive isotope of stable iodine​

  • Emits gamma and beta rays​

  • Half-life is 8 days​

• Used in Graves’ disease​

• Effect on the thyroid = destruction​

• Advantages and disadvantages of 131I therapy​

• Candidates​

  • Patients over 30​

  • Contraindicated in pregnancy and lactation​

• Action​

  • Produces clinical remission with destruction of thyroid gland

Non-radioactive Iodine

• Strong iodine solution (Lugol’s solution)​

• Used to suppress thyroid function in preparation for thyroidectomy​

Non-radioactive Iodine adverse effects

• Brassy taste​

• Burning sensation in the mouth and throat​

• Soreness of the teeth and gums​

• Frontal headache​

• Coryza (nasal inflammation & sneezing)​

• Salivation​

• Various skin eruptions

Hypothyroidism

• CAUSES

  • Hashimoto’s thyroiditis (autoimmune)​

  • Radiation​

  • Thyroid surgery

• F>M

• Congenital 1:4000 infants

• More common in Down’s syndrome

• Treatment goal:

  • Adequate dosage to compensate for thyroid defect​

  • Levothyroxine

Hypothyroidism clinical manifestations

• CNS:

  • Hypoactive reflexes

  • Slow speech, forgetfulness

• CV:

  • Cardiomegaly, heart failure, bradycardia

• Metabolic

  • Weight gain, ↑cholesterol, low temps

• GI:

  • Constipation, poor appetite

levothyroxine moa

• Synthetic form of thyroxine

• MOA: increase metabolism

  • increase HR, O2 consumption, respiratory rate, metabolism of fats, COOH & protiens

levothyroxine indications

Primary & Secondary causes of hypothyroidism

levothyroxine contraindications

Hyperthyroidism, MI

levothyroxine caution

Older adults with CAD, children

levothyroxine BBW

NOT indicated for weight loss or obesity

levothyroxine adverse effects

• Signs of hyperthyroidism

• Tachycardia, angina, tremors

levothyroxine drug to drug

• ↑antidepressants

• ↓antacids, iron supplements, OCP

• Those on warfarin- may dose adjustments

levothyroxine nursing considerations

EMPTY stomach, assess VS, medic alert bracelet, labs: LFT

Thyroid storm (thyrotoxic crisis)​

• life threatening

• Severe tachycardia, fever, dehydration, heart failure, coma​

• Inadequately treated hyperthyroidism​

• Treat symptoms

  • Propranolol commonly used

Myxedema

• life threatening

• Hypothermia, coma, V collapse, hypoventilation

• Electrolyte hyponatremia, hypoglycemia

• Treatment is supportive