THYROID DISEASE
Introduction: Thyroid disease is common and can mimic many other diseases so it should be considered in the differential diagnosis of many conditions. Hypothyroidism and hyperthyroidism are often (but not always) associated with enlargement of the thyroid gland (ie goiter) that can be either nodular or diffuse. Nodular and diffuse goiter can also occur without hypothyroidism or hyperthyroidism.
HYPOTHYROIDISM
Physical Manifestations:
ž Early Sx: weakness, fatigue, arthralgias, myalgias, headache, depression, cold intolerance, weight gain, constipation, menorrhagia, dry skin, coarse hair, brittle nails, delayed DTRS, diastolic HTN
ž Late Sx: slow speech, hoarseness, loss of outer third of eyebrows, myxedema (non-pitting thickened skin), periorbital puffiness, bradycardia, pleural/pericardial/peritoneal effusions
ž Myxedema coma (rare): hypothermia, hyporeflexia, bradycardia, hypotension, AMS (50% mortality)
Etiologies:
ž Primary (increased TSH, decreased T4)
o Goitrous (enlarged thyroid):
1. Hashimoto’s thyroiditis: common in women 20-60yo and due to automimmune destruction of the thyroid; associated with other autoimmune disorders
2. Iodine deficiency – common in rural areas but becoming less common with iodine supplementation of salt and other foods
3. Post-viral thyroiditis (De Quervains): less common, 6 weeks after a viral prodrome; tender goiter; labs may reveal hypo- hyper or euthyroid. Self-limiting but may require treatment. May also see elevated ESR and fever.
o Non Goitrous: surgical, s/p radioactive iodine/radiation, drugs like amiodarone
ž Secondary (decreased TSH, decreased T4) Hypothalamic or pituitary failure – very rare
Diagnostic Tests:
ž TSH, FT4
ž anti-thyroid peroxidase and anti-thyroglobulin antibodies if available (Hashimoto’s)
Tx:
ž Thyroid replacement with levothyroxine, start with 50-150mcg OD (1.5ug/kg/day), recheck TSH q6weeks and titrate until TSH <5; use a lower starting dose (.5ug/kg/day) if pt at risk for ischemic heart disease as levothyroxine can cause ischemia
ž If due to iodine deficiency, give Schiller’s iodine (1:30 dilute Lugol’s iodine) 2 drops OD x 6mo
HYPERTHYROIDISM
Clinical Manifestations
ž Restlessness, insomnia, heat intolerance, sweating, moist warm skin, fine hair, tachycardia, palpitations, AF, weight loss, increased freq of bowel movements, menstrual irregularities, hyperreflexia, osteoporosis, lid lag
ž Thyroid Storm: (seen with stress or surgery) delirium, fever, tachycardia, systolic hypertension (wide pulse pressure and low MAP), diarrhea (20-50% mortality)
Etiologies:
ž Primary (decreased TSH, increased T4)
· Goitrous (enlarged thyroid):
1. Toxic multi-nodular goiter – common; thyroid has multiple nodules
2. Graves disease – common in women 20-40yo, Genetic predisposition leads to antibodies to TSH receptors
· Unique Sx: diffuse, nontender goiter, proptosis (check sclera visibility above pupil), diploplia, pretibial myxedema
· Dx: thyroid stimulating antibodies
3. Thyroiditis (see above)
4. Toxic Adenomas: nodule producing T3/T4
· Non Goitrous: iodine-induced, struma ovarii (T3/T4 producing ovarion tumor)
ž Secondary (increased TSH, increased T4) - TSH-secreting pituitary tumor
Diagnostic Tests
ž Increased FT4/FT3; Decreased TSH (except for tumors)
ž Thyroid ultrasound – to assess for nodules
ž Radioactive iodine uptake scan
o Homogenous uptake—Graves
o Hetergeneous increase—multinodular goiter
o Single “hot nodule” —toxic adenoma
o No uptake—thyroiditis, iodine load, struma ovarii
Treatment
ž Start with B-Blockers (Propranolol): control tachycardia and decrease T4->T3 conversion
ž Graves/Thyroiditis: anti-thyroid medications or radiation
o PTU/methimazole/carbimazole (inhibit T3/T4 synthesis)
o Radioactive iodine
ž Nodular Hyperthyroidism: often treated with surgery but can also be treated with antithyroid medications or radiation
THYROID NODULES
ž The most common cause of thyroid nodules in our setting is multi-nodular goiterwhich is benign and common in areas of recently treated iodine deficiency.
ž Thyroid adenomas are also common.
ž Thyroid carcinoma is a rare but deadly cause of thyroid nodules. Features associated with thyroid carcinoma include
ž Age <20 or >70
ž h/o neck radiation therapy
ž large size
ž worrisome U/S findings (hypoechoic, solid, irregular borders, microcalcifications, central blood flow)
ž cervical LAN
ž FNA should be performed for
o Nodules >10mm with irregular borders, microcalcifications, or chaotic intranodular vascular spots
o Nodule of any size in a patient with h/o neck radiation therapy or a family history of MEN2 or medullary thyroid cancer
SICK EUTHYROID SYNDROME
ž Abnormal TFTs due to non-thyroidal disease. Seen in severe illness. TSH decreased or normal, T3/T4 decreased or normal. Does not require treatment but needs to be followed up
THYROID CASES
Case 1
27 yo female with a history of anemia presents to your clinic with 6 week history of fatigue and weakness. Patient states she misses her menses last month.
PMH: Anemia ’07 treated with albendazole
FH: Mother died in 40s from unknown causes
SH: Widow with 2 children. Peasant. No smoking or alcohol use.
Medications: Iron No drug allergies
ROS: +constipation, depression, hair loss, anorexia, dry skin and weight gain
PE: 36.4 BP 98/60 PR 56
Thin woman not pale but looks tired
HEENT: no oral lesions
Neck: diffuse, nontender thyromegaly, no palpable nodules/bruits, no lymphadenopathy
CV: bradycardia no murmurs
Pulm: clear
Abd: Soft nontender slightly distended, no organomegaly, hypoactive bowel sounds
Ext: 1+ pedal edema
Neuro: alert and oriented x3. patellar/brachioradialis/bicep reflexes 1+, nl strength, decreased sensation from toes to ankles.
CXR: normal
- What are your impression and what differential diagnoses would you consider?
Hypothyroidism. Also consider hypercortisolism (Cushings disease), primary hypogonadism, depression Emphasize that thyroid disease can mimic many other disease and, therefore, should often be on the differential diagnosis.
- Which symptoms/signs of hypothyroidism does this patient exhibit?
Review symptoms/signs in this patient and most common symptoms/signs in hypothyroidism.
- Does this patient have goiter? If so what type?
Yes. Goitre is just enlargement of the thyroid. This is a diffuse (not nodular) goiter.
- What are the most common causes of hypothyroidism?
Review etiologies according to their categories.
- What type of hypothyroidism is most likely in this patient given her history and physical examination?
Hashimoto’s (autoimmune) or iodine deficiency.
- What further investigations would you like to perform?
TSH, T3, T4, FBP, urine BCG to rule out pregnancy
The patients TSH returns elevated and the T3 and T4 are low.
- These findings confirm what type of hypothyroidism?
Primary.
- What would you have thought if the patient had a low (undetectable) TSH and a low T3/T4?
Secondary hypothyroidism, but emphasize that this is rare.
- What further investigation could you send if you wanted to confirm the diagnosis of Hashimoto’s?
Review antibodies and why these are present.
- How would you treat this patient? How would you monitor whether the treatment was sufficient?
Start thyroid replacement (levothyroxine) 50-100mcg OD. Followup in 6 weeks to check TSH. Also, symptoms should improve.
- If you do not treat the patient, what may happen? What is the most feared complication of untreated hypothyroidism.
Myxedema coma: hypothermia, hyporeflexia, bradycardia, hypotension, AMS (50% mortality) anti-thyroid peroxidase and anti-thyroglobulin antibodies,
Case 2
35 yo F with h/o HTN presents to H2 with awareness of heart beat. Patient states she has had rapid heart beat intermittently for the last month. On further questioning, she also states a new tremor when she picks up objects, blurry vision, diarrhea and weight loss. Patient states she had similar symptoms 2 yrs prior when stressed but this feels different. The patient is only taking aprinox for BP control. Denies fevers, chills, chest pain, nausea, vomiting, HA, urinary sx.
On evaluation, patient afebrile HR 120 BP 150/80. She is a thin woman and appears anxious. HEENT unremarkable. She has a irregularly enlarged, non-tender thyroid with multiple nodules, LAD or bruits. Cardiac exam notable for an irregularly, irregular pulse with a pulse deficit of 20. Lungs clear bilaterally. Abdomen benign. Patellar DTRS brisk and hyperreactive bilaterally. +fine tremors of hands bilaterally but no asterixis.
- What is your impression?
Hyperthyroidism.
- What signs/symptoms of hyperthyroidism does this patient exhibit?
Review symptoms/signs of hyperthyroidism in this patient and most common signs overall.
- Does this patient have a goiter? If so, what type?
Multinodular goiter.
- What are the most common causes of hyperthyroidism?
Review these according to categories above.
- What type of hyperthyroidism is most likely in this patient given her history and physical examination?
Toxic Multinodular Goitre
- What type of hyperthyroidism would be most likely if the patient had a uniformly enlarged, nontender thyroid gland and her eyes seem to be bulging so that you could see the sclera above the iris? How would you confirm this diagnosis?
Graves Disease, TSHr antibodies.
- What further investigations would you like to perform in this patient?
TSH, T3, T4 (thyroid ultrasound, radioactive iodine uptake scan if available)
The patients TSH returns low and the T3 and T4 are high.
- These findings confirm what type of hyperthyroidism?
Primary.
- What would you have thought if the patient had a high (undetectable) TSH and a high T3/T4?
Secondary hyperthyroidism, but emphasize that this is rare.
- Now that you have made the diagnosis of hyperthyroidism secondary to toxic, multinodular goiter, how will you treat the patient?
Review options of antithyroid medications vs radioactive iodine vs surgery. Note that surgery is common used here for toxic multinodular goiter but that medications should be first line for most other types of hyperthyroidism (like Graves).
- What other differential diagnosis do you have to consider in a patient with thyroid nodules? What factors make this more or less likely? How would confirm this diagnosis?
Review information on thyroid carcinoma.
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