A.7 Hyperthyroidism Flashcards
A.7 Hyperthyroidism
define
a condition characterized by the overproduction of thyroid hormones by the thyroid gland; can cause thyrotoxicosis
A.7 Hyperthyroidism
What is Overt Hyperthyroidism
↓ Serum TSH levels with ↑ serum free T4 and/or T3 levels
Patients typically experience symptoms of thyrotoxicosis.
A.7 Hyperthyroidism
What is Subclinical Hyperthyroidism
↓ Serum TSH levels with normal serum free T4 and T3 levels
Patients are normally asymptomatic or mildly symptomatic.
May progress to overt hyperthyroidis
A.7 Hyperthyroidism
Epidemiology
Sex: ♀ > ♂ (5:1)
Age range at presentation [10]
Graves disease: 20–30 years of age
Toxic adenoma: 30–50 years of age
Toxic MNG: peak incidence > 50 years of age
A.7 Hyperthyroidism
Etiology of Hyperfunctioning thyroid gland
Hyperfunctioning thyroid gland
- Graves disease (∼ 60–80% of cases)
- Toxic MNG (∼ 15–20% of cases)
- Toxic adenoma (3–5% of cases)
- TSH-producing pituitary adenoma (thyrotropic adenoma)
- hCG-mediated hyperthyroidism: e.g., gestational transient thyrotoxicosis (GTT), gestational trophoblastic disease (GTD)
A.7 Hyperthyroidism
Etiology of Destruction of the thyroid gland (destructive thyroiditis)
- Thyroiditis
- Subacute granulomatous thyroiditis (de Quervain thyroiditis)
- Subacute lymphocytic thyroiditis (e.g., postpartum thyroiditis)
- Drug-induced thyroiditis (e.g., amiodarone, lithium)
- Contrast-induced thyroiditis (Jod-Basedow phenomenon)
- Hashitoxicosis (see “Hashimoto thyroiditis”)
- Radiation thyroiditis
- Palpation thyroiditis: due to thyroid gland manipulation during parathyroid surgery.
- Riedel thyroiditis
A.7 Hyperthyroidism
Etiology of Ectopic Hormone Production
Struma ovarii
Metastatic follicular thyroid carcinoma
A.7 Hyperthyroidism
pathophys of Hypothalamic-pituitary-thyroid axis
Disorders of the thyroid gland → excess production of T3/T4 → compensatory decrease of TSH
Thyrotropic adenoma → ↑ TSH levels → ↑ T3/T4 levels
A.7 Hyperthyroidism
Clinical General
- Heat intolerance
- Excessive sweating because of increased cutaneous blood flow
- Weight loss despite increased appetite
- Frequent bowel movements (because of intestinal hypermotility)
- Weakness, fatigue
A.7 Hyperthyroidism
Skin Clinical Features
- Infiltrative dermopathy, especially in the pretibial area (pretibial myxedema)
- Onycholysis - A separation of the nail from the nail bed
An early cutaneous manifestation of hyperthyroidism
Thickened nails with distal white discoloration and separation of the nail plate
Initially develops in the fourth fingers, but can involve all nails, including the toenails - Thyroid acropachy: nail clubbing seen in late stages of Graves disease
A.7 Hyperthyroidism
Eye Clinical Features
Lid lag: caused by adrenergic overactivity, which results in spasming of the smooth muscle of the levator palpebrae superioris
A.7 Hyperthyroidism
Cardiovascular Clinical
Tachycardia
Palpitations, irregular pulse (due to atrial fibrillation/ectopic beats)
Hypertension with widened pulse pressure
Systolic pressure is increased due to increased heart rate and cardiac output.
Diastolic pressure is decreased due to decreased peripheral vascular resistance.
Thyrotoxicosis-induced cardiac failure: elderly patients often present with features of cardiac failure (e.g., pedal edema, exertional dyspnea).
Abnormal hheart rhythms, including atrial fibrillation
Chest pain
A.7 Hyperthyroidism
Musculoskeletal Clinical
Fine tremor of the outstretched fingers
Hyperthyroid myopathy: a condition of muscle weakness, pain, and atrophy associated with hyperthyroidism (e.g., from Graves disease, thyroiditis)
A.7 Hyperthyroidism
Endocrine Features
Female: oligomenorrhea, amenorrhea, anovulatory infertility, dysfunctional uterine bleeding
Male: gynecomastia, decreased libido, infertility, erectile dysfunction
Glucose intolerance
↓ Insulin sensitivity of peripheral tissue
Impaired insulin secreti
A.7 Hyperthyroidism
Neuropsychiatric system
Anxiety
Emotional instability
Depression
Restlessness
Insomnia
Tremoulousness (results from the hyperadrenergic state)
Hyperreflexia
A.7 Hyperthyroidism
DX
Thyroid function tests
- Thyroid-stimulating hormone (TSH) level (initial screening test): Typically low/undetectable; a normal TSH level usually rules out hyperthyroidism.
- Free T4 (FT4) and total T3 levels: Typically both elevated; indicated when thyrotoxicosis is strongly suspected or TSH is abnormal
CBC: leukocytosis and/or mild anemia
BMP
- Hyperglycemia
- Mild hypercalcemia
Liver chemistries: mildly elevated AST, ALT, ALP, and bilirubin
Serum cholesterol: decreased total cholesterol, LDL, and HDL
ESR: typically elevated (> 100 mm/hour) in subacute thyroiditis
A.7 Hyperthyroidism
ECG
Tachycardia
Atrial fibrillation
LBBB and ECG signs of LVH in patients with dilated cardiomyopathy
