thyroid

Replacement of or supplementation to endogenous thyroid hormones.
Principal effect is increasing metabolic rate of body tissues:
- Promote gluconeogenesis,
- Increase utilization and mobilization of glycogen stores,
- Stimulate protein synthesis,
- Promote cell growth and differentiation,
- Aid in the development of the brain and CNS.
Contains T₃ (triiodothyronine) and T₄ (thyroxine) activity.

Therapeutic effects:

Replacement in deficiency states with restoration of normal hormonal balance.

Pharmacokinetics ⬆ ⬇

Absorption: Levothyroxine is variably (50–80%) absorbed from the GI tract. Liothyronine is well absorbed.

Distribution: Distributed into most body tissues. Thyroid hormones do not readily cross the placenta; minimal amounts enter breast milk.

Metabolism/Excretion: Metabolized by the liver and other tissues. Thyroid hormone undergoes enterohepatic recirculation and is excreted in the feces via the bile.

Half-Life: T₃ (liothyronine)—1–2 days; T₄ (thyroxine)—6–7 days.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
Levothyroxine PO	unknown	1–3 wk	1–3 wk
Liothyronine PO	unknown	24–72 hr	72 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Recent MI;
Hyperthyroidism.

Use Cautiously in:

Cardiovascular disease (initiate therapy with lower doses);
Severe renal insufficiency;
Uncorrected adrenocortical disorders;
Geri: Geriatric patients are extremely sensitive to thyroid hormones; initial dosage should be .

Adv. Reactions/Side Effects ⬆ ⬇

Usually only seen when excessive doses cause iatrogenic hyperthyroidism

CV: arrhythmias, tachycardia, angina pectoris

GI: abdominal cramps, diarrhea, vomiting

Derm: hyperhidrosis

Endo: hyperthyroidism, menstrual irregularities

Metab: weight loss, heat intolerance

MS: accelerated bone maturation in children

Neuro: insomnia, irritability, headache

Interactions ⬆ ⬇

Drug-drug:

Bile acid sequestrants↓ absorption of orally administered thyroid preparations.
Alters the effectiveness of warfarin (INR will ↑ with thyroid hormone supplementation).
May ↑ requirement for insulin or oral hypoglycemic agents in diabetics.
Concurrent estrogen therapy may ↑ thyroid replacement requirements.
↑cardiovascular effects with adrenergics (sympathomimetics).

Foods or supplements containing high amounts of calcium, iron, magnesium, or zinc may bind thyroid hormones and prevent complete absorption.

Route/Dosage ⬆ ⬇

Each 1 gr = 60 mg and is equivalent to approximately 100 mcg of levothyroxine (T₄) or 25 mcg of liothyronine (T₃)

Thyroid

PO (Adults and Children ): Hypothyroidism—60 mg/day; ↑ q 4 wk by 30 mg; usual maintenance dose is 60–120 mg/day. Myxedema/hypothyroidism with cardiovascular disease—15 mg/day initially; ↑ by 30 mg/day q 2 wk, then may ↑ by 30–60 mg q 2 wk; usual maintenance dose is 60–120 mg/day.
PO Geriatric Patients ): 7.5–15 mg/day initially; may double dose q 6–8 wk until desired effect is obtained.

Availability ⬆ ⬇

Tablets (regular):
15 mg
13.45
100
30 mg
15.79
100
60 mg
17.53
100
90 mg
27.66
100
120 mg
32.41
100
180 mg
51.43
100
240 mg
77.09
100
300 mg
95.57
100
15 mg; 30 mg; 60 mg; 90 mg; 120 mg; 180 mg; 240 mg; 300 mg

Assessment ⬆ ⬇

Assess apical pulse and BP prior to and periodically during therapy. Assess for tachyarrhythmias and chest pain.
Pedi: Monitor height, weight, and psychomotor development.

Lab Test Considerations:

Monitor thyroid function studies prior to and during therapy.
- Monitor blood and urine glucose in diabetic patients. Insulin or oral hypoglycemic dose may need to be increased.

Toxicity and Overdose:

Overdose is manifested as hyperthyroidism (tachycardia, chest pain, nervousness, insomnia, diaphoresis, tremors, weight loss). Usual treatment is to withhold dose for 2–6 days. Acute overdose is treated by induction of emesis or gastric lavage, followed by activated charcoal. Sympathetic overstimulation may be controlled by antiadrenergic drugs (beta blockers), such as propranolol. Oxygen and supportive measures to control symptoms such as fever are also used.

Implementation ⬆ ⬇

Administer as a single dose, preferably before breakfast to prevent insomnia.
- Initial dose is low, especially in geriatric and cardiac patients. Dose is increased gradually, based on thyroid function tests.
- For patients with difficulty swallowing, tablets can be crushed and placed in 5–10 mL of water and administered immediately via dropper or spoon; do not store suspension.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed at the same time each day. Take missed doses as soon as remembered unless almost time for next dose. If more than 2–3 doses are missed, notify health care professional. Do not discontinue without consulting health care professional.
- Explain to patient that medication does not cure hypothyroidism; it provides a thyroid hormone supplement. Therapy is lifelong.
- Advise patient to notify health care professional if headache, nervousness, diarrhea, excessive sweating, heat intolerance, chest pain, increased pulse rate, palpitations, weight loss >2 lb/wk, or any unusual symptoms occur.
- Caution patient to avoid taking other medications concurrently with thyroid preparations unless instructed by health care professional.
- Instruct patient to inform health care professionals of thyroid therapy.
- Emphasize importance of follow-up exams to monitor effectiveness of therapy. Thyroid function tests are performed at least yearly.
Pedi: Discuss with parents the need for routine follow-up studies to ensure correct development. Inform patient that partial hair loss may be experienced by children on thyroid therapy. This is usually temporary.

Evaluation/Desired Outcomes ⬆ ⬇

Resolution of symptoms of hypothyroidism and normalization of hormone levels.

US Brand Names ⬆ ⬇

Armour Thyroid, Westhroid

Pot. Nursing Diagnoses ⬆ ⬇

Deficient knowledge, Relate med(Patient/Family Teaching)

Code ⬆

NDC Code

43063- PD-Rx Pharmaceuticals, Inc.
- 43063-345- Armour Thyroid
  - 43063-345-30- 30 TABLET in 1 BOTTLE, PLASTIC (43063-345-30)

62106- Seroyal USA
- 62106-7140- THYROIDINUM
  - 62106-7140-4- 10 TUBE in 1 CARTON (62106-7140-4) > 140 GRANULE in 1 TUBE

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇