Thyroid Pathophysiology Flashcards
Describe the epidemiology of hypothyroidism:
10M Americans: Higher risk in women, especially as they age past 40
What are the etiologies of hypothyroidism? Primary (4), central and transient
Primary: Autimmune (Hasimoto’s), thyroidectomy, dysgenesis/agenesis, defects in biosynthesis
Central: Pituitary/hypothalamic
Transient: hypothyroid phase of thyroiditis
What do you see on pathology for lymphocytic thyroiditis (Hashimoto’s)? (2)
Follicular atrophy
Infiltration with lymphocytes
Are Hashimoto’s patients more susceptible for any other diseases?
Yes, other autoimmune disorders
What is the clinical significance of mild thyroid failure? Is treatment indicated?
Serum level of 5
What is myxedema coma?
Which patients will exhibit myxedema coma?
Severe hypothyroidism seen in elderly patients with pre-existing hypothyroidism and acute illness.
Characterized by hypothermia and coma with 20-25% mortality
What are the clinical features myxedema coma?
What lab values would you expect?
Mental status changes : stupor, confusion, coma and hypothermia
Labs: high FSH with low T4, total T3, hyponatremia, hypercholesterolemia, high LDH, hypoxemia
How is myxedema coma managed?
Treat precipitating factors.
GIVE STEROIDS before Thyroid hormone–>supplemental thyroid hormone will increase glucocorticoid metabolism
How is hypothyroidism treated?
Levothyroxine sodium (LT4)– Take one pill daily to achieve normal TSH
What are causes of hyperthyroidism? (5)
Overproduction: Graves disease, toxic solitary nodule, toxic multi nodular goiter
Leakage of thyroid hormone: autoimmune thyroiditis, viral thyroiditis
What are causes of thyroiditis? (4)
What are possible courses? (3)
Causes: Autoimmune, bacterial/fungal, viral, toxic
Course: Hyperthyroidism (leakage of stored thyroid hormone), return to euthyroid state, swing to transient hypothyroidism (while damaged follicular cells recover)
List some clinical symptoms of hyperthyroidism
Appetite change, shortness of breath, fatigue, headache, heat intolerance, hyperactivity, increased perspiration, irritability, menstrual disturbance, nervousness, palpitations, muscle weakness, sleep disturbance, tremor, weakness, weight change
List some signs of hyperthyroidism
Goiter, hyperactivity, hyperreflexia, muscle weakness, systolic hypertension, tachycardia/arrhythmia, tremor, warm/moist/smooth skin
What is pathophysiology of Graves disease?
Autoimmune binding to TSH receptor in pituitary– antibody is stimulating.
What is histology of Grave’s disease?
Hyperplasia of follicular cells– lots of colloid but it’s irregular and more papillary.
Describe the ophtho symptoms of hyperthyroidism (3). Compare them to graves ophthalmopathy (3)
Hyperthyroidism: Lid lap, lid retraction, stare due to increased adrenergic tone to levator palpibrae
Graves: Proptosis, diplopia, inflammatory changes
Describe rare symptoms of Grave’s disease: dermatologic
Dermatological: myxedema in lower leg
Acropachy: clubbing of fingers, separation of nail plate from bed
How do you differentiate between causes of hyperthyroidism?
What is the normal value for the test?
Radioiodine uptake
Normal uptake is 15-35%
What are the results of radioiodine uptake for Graves disease vs. Thyroiditis?
Graves: Elevated uptake
Thyroiditis: Decreased uptake
What are the treatment options for Grave’s disease?
- Antithyroid drugs
- Radioiodine ablation
- Surgery
What are the antithyroid drugs (2) and what are their side effects (3)?
Methimazole, PTU
AE: rash, agranulocytosis, hepatitis
Describe the efficacy and side effects of radioactive iodine (3)
It’s an oral therapy to destroy the thyroid that takes 3-6 months.
AE: teratogenic, hypothyroid, worsens ophthalmopathy
When is a thyroidectomy performed (2)?
What is main side affect?
Thyroidectomy for large toxic nodular goiters with compressive symptoms OR patients who have had severe AE with antithyroid drugs
Hypothyroidism results.
What is a thyroid storm? Describe it’s cause, incidence and mortality
Thyroid storm is extreme manifestation of thyrotoxicosis– result of tissue exposure to excessive thyroid hormone.
Incidence is 1-2% with vastly decreasing mortality.
What is the clinical manifestation of a thyroid storm? (5)
Really some might fuck tonight:
Restlessness, Sweating, Mental status change, fever, tachycardia
What is a goiter? What criteria do you use to describe it? (3)
A goiter is an enlarged thyroid gland.
Prevalence: endemic/non-endemic
Structure: Diffuse vs. nodular
Function: Toxic or non-toxic
What is the etiology of goiters?
Multiple– thyroiditis, cancer, nodules etc.
What is most common cause of goiters? How common are they?
Goiter is most commonly caused by iodine deficiency.
It is in >10% population and is present in 4-7% US population
How common are thyroid nodules? What are risk factors? (3)
Palpable in 6% women 1.5% men aged 30-60.
Risk factors include old age, women, gender susceptibility
What is the differential diagnosis for thyroid nodules? What are the relative frequencies?
Malignant (5-10%)– papillary (75%), follicular (15%), medullary
Benign (90%)
What are things you look for to evaluate thyroid nodules in history?
Neck irradiation, family history, age, gender, duration, local symptoms, presence of coexistent benign thyroid disease
What factor is important in radiation and thyroid cancer?
How long is latency period? How long does risk last?
Age at irradiation– there is no increase in risk if exposed after 16-18.
Latent period is 10-20 years, but risk if lifelong following exposure.
What are things you look for in physical exam of thyroid nodules? (3)
Fixation to adjacent structures
Adenopathy
Firm nodular consistency
When do you need to do an FNA? Why?
If TSH is normal or high. Low TSH or “hot” nodules have low likelihood of malignancy.
How many nodules are “cold”?
What do you with cold nodules?
Cold or hypofunctioning nodules make up 90% of nodules.
You follow up with FNA
How many patients with atypical thyroid nodules receive surgery? How many of those are malignant?
30% of patients with atypical thyroid nodules go to surgery.
Only 1/3 have cancer.
