Definition
A.If the thyroid-stimulating hormone (TSH) level is too high, the thyroid gland is not producing enough thyroid hormone, specifically T4 and possibly T3. This is called hypothyroidism.
B.Develops when the thyroid gland produces less than the normal amount of thyroid hormones. This leads to low serum levels of T4.
C.Results in the slowing of several bodily functions.
D.The main autoimmune cause of hypothyroidism is Hashimoto’s disease.
Incidence
A.Hypothyroidism affects approximately 10 million people.
B.It affects approximately 10% of women and 3% of men in the outpatient setting.
C.Inhibits natural mechanism of metabolism in the body affecting many organ systems. Also associated with increased serum cholesterol levels, which may increase the risk for atherosclerosis and heart disease.
Pathogenesis
A.Insufficient production of thyroid hormone from thyroid gland.
B.Three causes.
1.Primary: Occurs at the thyroid.
2.Secondary: Results from problems with the pituitary.
3.Tertiary: Results from problems at the level of the hypothalamus.
Predisposing Factors
A.Age and sex.
B.Family history.
C.Any autoimmune disorder: Autoimmune thyroiditis.
D.Subacute thyroiditis.
E.Radioactive iodine treatment.
F.Spontaneous onset.
G.Thyroid surgery or medications.
H.Postpartum thyroiditis.
I.Congenital condition.
Subjective Data
A.Common complaints/symptoms.
1.Weight gain, fatigue, forgetfulness, dry hair/nail changes, cold intolerance, menstrual irregularities.
B.Common/typical scenario.
1.Patient presents with persistent fatigue and inability to lose weight. The patient will complain that he or she just does not feel right.
C.Family and social history.
1.May have a familial link.
D.Review of systems.
1.Constitution—ask about recent viral infections, pervasive fatigue, drowsiness, forgetfulness, learning difficulties.
2.Dermatological—dry brittle hair and nails, itchy skin.
3.Psychological—recent depression, feeling sadness, decreased libido, irritability.
4.Endocrine—cold intolerance, menstrual irregularities, miscarriages.
5.Musculoskeletal—muscle cramps, soreness.
Physical Examination
A.Cardiovascular—low blood pressure, bradycardia, fluid retention.
B.HEENT—periorbital edema, assess for presence of goiter, dysphagia, eyebrow hair loss, possible scalp hair loss.
C.Neuro/musculoskeletal—lower extremity fluid retention, myalgia, arthralgia, hyporeflexia.
D.Dermatological—dry skin, coarse.
Diagnostic Tests
A.TSH (0.4–5 uIU/mL).
B.Free T4 (0.8–1.8 ug/dL).
C.Thyroid antibodies.
1.Thyroid peroxidase (TPO) level (<35 IU/mL).
Differential Diagnosis
A.Anemia.
B.Addison’s disease.
C.Anovulation.
D.Dysmenorrhea.
E.Cardiac tamponade.
F.Pericardial effusion.
G.Chronic fatigue syndrome.
H.Depression.
I.Thyroiditis.
J.Euthyroid sick syndrome.
K.Goiter.
L.Hypothermia.
M.Constipation.
N.Infertility.
O.Iodine deficiency.
P.Menopause.
Q.Hyperlipidemia.
R.Pituitary disorders.
Evaluation and Management Plan
A.General plan.
1.Normalize thyroid levels by starting thyroid hormone replacement therapy.
2.Routine laboratory testing every 6 weeks to adjust dose accordingly until stabilized.
B.Patient and family teaching.
1.Teach patient signs and symptoms of hypothyroidism and when to call provider, including increase in fatigue, unexplained weight gain and fluid retention, increase in hair loss, arthralgias, and myalgias.
2.Labs must be checked every 6 weeks for a period of time until the medications can be normalized to patient tolerance and TSH goal is reached.
C.Pharmacology.
1.Treatment consists of administering the synthetic thyroid hormone levothyroxine.
a.Dose is based on weight in kilograms multiplied by 1.6 and can be administered orally or intravenously in the hospital setting at 50% to 80% of the PO dose. It should be taken on an empty stomach with no food, no other medications or caffeine for 1 hour, and no supplements for 4 hours.
Follow-Up
A.Ensure patient adherence to treatment regimen.
B.Stress the importance of taking medication daily at approximately the same time.
C.Stress the importance of laboratory checks of TSH level every 6 to 8 weeks.
Consultation/Referral
A.Once discharged, referral to an outpatient endocrinologist is recommended.
Special/Geriatric Considerations
A.Keep TSH levels for geriatric patients in the midrange to avoid the incidence of cardiac side effects such as atrial fibrillation or tachycardia.
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