Drug Therapy for Thyroid Disorder

What three hormones does the thyroid gland produce?

thyroxine (T4), thriiodothyronine (T3), calcitonin

What are the functions of thyroid hormones

• increases rate of cellular metabolism + oxygen consumption + increase in heat production

• increases heart rate + force of contraction + systemic vascular resistance + increased cardiac workload

• increased carb metabolism

• increased fat metabolism

• inhibition of pituitary secretion of TSH

what is hypothyroidism

Causes: disease or destruction of thyroid gland —> inadequate production of thyroid hormones

What conditions?

• hashimoto’s disease

• iodine deficiency

• pituitary tumor

• destruction or removal of thyroid: radiation therapy or surgery

• treatment of hyperthyroidism

• treatment with aminodarone, lithium, or iodine preparations

what is hyperthyroidism

Causes: excessive synthesis and secretion of thyroid hormones

What conditions?

• Graves disease

• enlarged thyroid gland with increased number of cells

• nodular thyroid goiter

• overtreatment of thyroid drugs

• thryoid carcinoma

• pituitary adenoma

Clinical manifestations of hypothyroidism

CV: decreased CO, HR, BP, heart failure, anemia, cardiac enlargement

CNS: apathy, lethargy, slow speech, hypoactive reflexes, forgetful, mental sluggishness, drowsiness

Metabolic: cold intolerance, subnormal body temp, increased cholesterol and weight gain

GI: decreased appetite

MSK: fatigue, weakness, vague pain

Integ: dry, coarse, thick skin; puffy face and eyelids; dry thin hair, thick hard nails

Reproductive: prolonged menstrual period, infertility, decreased libido

• increased susceptibility to infection

• slow drug metabolism

Clinical manifestations of hyperthyroidism

CV: increased CO, HR, blood volume, dysrhythmias, heart failure

CNS: nervousness, emotional instability, restlessness, hyperactive reflexes, anxiety, insomnia

Metabolic: heat intolerance, low grade fever, weight loss

GI: increased appetite, cramps, diarrhea and NV

MSK: fatigue, weakness, muscle apathy and tremors

Integ: moist, warm skin, flushed skin, increased sweating, localized edema around eyes, exophthalmos, soft hair and nails

Reproductive: amenorrhea or oligomenorrhea

• increased susceptibility to infections

• dyspnea

• horse rapid speech

• polyuria

Severe hypothyroidism clinical manifestations

myxedema coma

• severe, life threatening hypothyroidism characterized by

  • coma,

  • hypothermia,

  • cardiovascular collapse,

  • hypoventilation,

  • and severe metabolic disorders (hyponatremia, hypoglycemia, and lactic acidosis)

Clinical manifestation of severe hyperthyroidism

thyroid storm/thyrotoxic crisis

• rare but severe complication characterized by extreme symptoms

  • tachycardia

  • fever

  • dehydration

  • heart failure and coma

  • exopthalamos

levothyroxine therapeutic use

used as hypothyroidism treatment

• standard care for long term treatment of hypothyroidism

• be consistent, do not change brands, do not take more than prescribed and do not stop abruptly

levothyroxine mechanism of action

synthetic preparation of thyroxine (T4) replacement therapy

• take in morning on empty stomach 1 hr before meal

levothroxine contraindications

• BLACK BOX WARNING = not to be prescribed for obesity or weight loss

• caution with cardiovascular disease

• hold off med if HR is greater than 100 beats/min

• caution with addison’s disease, lactation, angina

levothyroxine adverse effects

• CV events most likely in elderly patients or those with heart disease

propylthiouracil therapeutic uses

anti-thyroid agent for hyperthyroidism

• for preoperative preparation for thyroidectomy

• before and after radioactive iodine therapy

• treatment of thyroid storm

propylthiouracil mechanism of action

inhibits the production of thyroid hormones of peripheral conversion of T4 to T3

Contraindications of propylthiouracil

• BLACK BOX WARNING = severe liver injury resulting in death or acute liver failure. may occur within 6 months of treatment

• not recommended for children

adverse effects of propylthiouracil

• hematologic effects = leukopenia, agranulocytosis and puts patients at risk for sepsis (early symptoms could be sore throat and fever)

• hypoprothrombinemia

propylthiouracil nursing considerations

• may increase effect of anticoagulants

• take consistently - do not change how you take the medication

• therapeutic effects —> 1-2 weeks

• euthyroid state —> 6-8 weeks

• may need to reduce or omit sources of iodine