Thyroid Disorders

Question 1

Hyperthyroidism: definition and etiology

Answer 1

Excessive levels of circulating thyroid hormone
Causes
Toxic diffuse goiter (Graves’ disease)
Hyperfunctioning thyroid nodule
Anterior pituitary disorders
Toxic MNG (Plummer’s disease)
Iodine-induced disease (e.g., amiodarone)

Question 2

Hyperthyroidism: S/S

Answer 2

• Tachycardia
• Arrhythmias
• Palpitations
• Weight loss
• Diarrhea
• Nausea and vomiting
• Sweating (hyperhydrosis)
• Flushing
• Hair loss
• Oligomenorrhea in women
• Impotence in men
• Decreased libido in men
• Restlessness/insomnia
• Emotional lability

Question 3

Labs in Hyperthyroidism:

Answer 3

TFTs
TSH is low (suppressed)
T3 and T4 are high

Question 4

TX options in Hyperthyroidism:

Answer 4

-Symptom relief
Propranolol: start 80–160 mg daily divided BID
Atenolol: if history of RAD or risk for hypoglycemia
-Definitive treatment
Antithyroid drugs (response takes 4–8 weeks)
Methimazole: start 15–30 mg daily or divided TID
Propylthiouracil (PTU): risk of hepatoxicity
-Radioactive iodine
-Surgery

Question 5

Monitoring in Hyperthyroidsim:

Answer 5

• Check TSH/FT4 every three weeks until euthyroid
• Goal is normalization of TSH
• Baseline and periodic WBC for first 4 months
• Mild leukopenia is common
• Decrease medication for WBC less than 1,500
• Then 3 months, 6 months, annually
• May become hypothyroid as a result of treatment
• TSH is first indicator

Question 6

Hypothyroidism: S/S

Answer 6

• CV: bradycardia
• Heme: amenia (poor absorption, decreased erythropoetan, or EPO)
• GI: constipation, weight gain, elevated lipids, fluid retention
• Skin: dry flaky skin, brittle hair, slow wound healing, cold
• Reproductive: anovulation, decreased libido, SAB
• Renal: increased body water, dilutional hyponatremia, decreased EPO
• Neuro: confusion, memory loss, night blindness, ataxia
• MSK: joint aches and stiffness, decreased DTRs
• Miscellaneous: fatigue and depression

Question 7

Primary Hypothyroidism:

Answer 7

Primary: defective thyroid hormone synthesis
Elevated TSH
Low T3 and T4
Causes: Hashimoto’s, subacute thyroiditis
Less common: congenital, iodine deficiency

Question 8

Secondary Hypothyroidism:

Answer 8

Secondary: pituitary or hypothalamic failure
Low TSH, T3, and T4
Causes: Cushing’s, pituitary adenoma, acromegaly

Question 9

TX of Hypothyroidism:

Answer 9

*All patients with TSH greater than 10 mcU/mL
Goals
-Correction of hypometabolic state
-Resolution of symptoms
-Normalization of TSH and FT4
-TSH target 0.3–3.0 mcU/mL
Synthetic thyroid hormone replacement
Levothyroxine (T4)
Liothyronine (T3)
Liotrix (4:1 ratio mix of T4 and T3)

Question 10

Levothyroxine: pt education, initiation of drug and monitoring

Answer 10

Start 50–100 mcg daily for young healthy patients
Start 12.5–50 mcg daily if over 50 years of age or heart disease
** Provide education: must take medication on an empty stomach
-Recheck TSH and FT4 in 4 to 6 weeks
If clinically euthyroid, recheck 4 to 8 weeks
-Still clinically hypothyroid with elevated TSH
Increase by 50 mcg a day if young and healthy
Increase by 25 mcg a day if over 50 years of age or heart disease
Recheck 4 to 8 weeks again
-If euthyroid on two checks, TSH at 6 months, then yearly
* Refer to Endocrine if TSH doesn’t normalize

Question 11

Hypothyroidism and pregnancy:

Answer 11

• Check TSH and FT4 at 8 week’s and 6 month’s gestation
• May need to increase maintenance dose of levothyroxine by 25%
• If so, check TSH every 6 weeks