Thyroid Disorders Flashcards
the state of thyroid hormone excess
thyrotoxicosis
the result of excessive thyroid function
hyperthyroidism
Primary Hyperthyroidism
Graves Disease Toxic Multinodular Goiter Toxic Adenoma functioning thyroid carcinoma metastases Activating mutation of TSH receptor McCune-Albright syndrome Struma ovarii Drugs: iodine excess (Jod-Basedow phenomenon)
Thyrotoxicosis without Hyperthyroidism
Subacute thyroiditis
Silent thyroiditis
Other causes of thyroid destruction: amiodarone, radiation, infarction of adenoma
Secondary Hyperthyroidism
TSH-secreting pituitary adenoma
Thyroid Hormone Resistance Syndrome: some patients may have symptoms of thyrotoxicosis
Gestational thyrotoxicosis
MINOR risk factor for Graves’ disease
smoking
MAJOR risk factor for the development of ophthalmopathy
ophthalmopathy
Antibodies that (+) TSH receptor
thyroid stimulating immunoglobulin (TSI)
Play a major role in thyroid-associated ophthalmopathy
cytokines
the release of cytokines such as interferon γ (IFN-γ), tumor necrosis factor (TNF), and interleukin-1 (IL-1) –> fibroblast activation and ↑ synthesis of glycosaminoglycans that trap water –> muscle swelling
LATER - there is irreversible fibrosis of the muscles
Features of thyrotoxicosis may be subtle or masked
apathetic thyrotoxicosis
Symptoms of Thyrotoxicosis
- hyperactivity, irritability, dysphoria
- heat intolerance and sweating
- palpitations
- fatigue and weakness
- weight loss w/ increased 6. appetite
- diarrhea
- polyuria
- oligomenorrhea, loss of libido
Signs of Thyrotoxicosis
- tachycardia
- afib in elderly
- tremor
- goiter
- warm, moist skin
- muscle weakness, proximal myopathy
- lid retraction or lag
- gynecomastia
MC cardiovascular manifestation
sinus tachycardia
Thyroid gland in patients w/ Grave’s disease
usually diffusely enlarged to 2 to 3x its normal size
consistency - firm, but NOT nodular
thrill or bruit
Earliest manifestations of Graves’ ophthalmopathy
sensation of grittiness
eye discomfort
excess tearing
Most serious manifestation of Graves’ ophthalmopathy
compression of the optic nerve at the apex of the orbit –> PAPILLEDEMA; peripheral field defects; permanent loss of vision (if left untreated)
NO SPECS
0 No signs or symptoms
1 Only signs (lid retraction or lag), no symptoms
2 Soft tissue involvement (periorbital edema)
3 Proptosis (> 22mm)
4 Extraocular muscle involvement (diplopia)
5 Corneal involvement
6 Sight loss
Most frequent over the anterior and lateral aspects of the lower leg (pretibial myxedema)
Thyroid dermopathy
Refers to a form of clubbing found in <1% of patients with Graves’ disease
Thyroid acropachy
Lab result of hyperthyroidism
↓ TSH level
↑ total and unbound thyroid hormone levels
May be useful if the diagnosis is unclear clinically but is not needed routinely
Measurement of TPO antibodies or TBII
Diagnosis of Graves Disease
biochemically confirmed
thyrotoxicosis
diffuse goiter on palpation
ophthalmopathy
dermopathy
often a personal or family history of autoimmune disorders
Distinguish the diffuse, high uptake of Graves’ disease from destructive thyroiditis, ectopic thyroid tissue, and factitious thyrotoxicosis, as well as diagnosing a toxic adenoma or toxic MNG
radionuclide (99mTc, 123I, or 131I) scan and uptake of the thyroid
Thyrotoxicosis w/ ELEVATED RAI uptake
Graves disease
Toxic adenoma
Toxic MNG
Thyrotoxicosis w/ LOW RAI uptake
Painless (silent) thyroiditis
Amiodarone-induced thyroiditis
Subacute thyroiditis (granulomatous, de Quervain’s)
Others: thyrotoxicosis factitia, struma ovarii
Frequent finding in patients with hyperthyroidism
fine tremor
Drugs that DECREASE serum T4 and T3
glucocorticoids androgens L-asparaginase salicylates mefenamic acid antiseizure medications - phenytoin, carbamazepine furosemide
Conditions that DECREASE serum T4 and T3
genetic factors
acute and chronic illnesses
Low TSH, Low FT4
secondary/central hypothyroidism
sick euthyroid syndrome
Low TSH, Normal FT4
subclinical hyperthyroidism (if normal FT3)
T3 toxicosis (high FT3)
early phase of treatment of thyrotoxicosis w/ antithyroid medications
Low TSH, High FT4
Primary Thyrotoxicosis: Graves’ disease, MNG, toxic adenoma
Destructive thyroiditis, excess iodine intake, excess thyroid hormone
Reduces thyroid hormone synthesis
antithyroid drug
Reduces the amount of thyroid tissue
radioiodine treatment or thyroidectomy
Antithyroid drug indicated in EARLY gestation (1st trimester), THYROID STORM and those experiencing adverse reactions to methimazole
Propylthiouracil
MOA of propylthiouracil
(-) thyroid peroxidase (TPO), reducing oxidation and organification of iodide
Thioamide that inhibits peripheral deiodinization of T4 to T3
Propylthiouracil
Most DANGEROUS complication of thioamide use
AGRANULOCYTOSIS- severe reduction in the number of white blood cells (granulocytes) in the circulating blood
MOST COMMON adverse effect of thioamide use
MACULOPAPULAR PRUTITIC RASH
Antithyroid drug of choice in adults and children
Methimazole
Inhibits hormone release through inhibition of thyroglobulin proteolysis and is often used to decrease the size and vascularity of the hyperplastic gland (used in preoperative preparation for surgery)
Iodide
PTU dosage
100-200 mg PO q6-8h (initiation)
50-100 mg PO/day (maintenance)
Methimazole dosage
10-20 mg PO q8-12 h (initiation)
2.5 - 10 mg PO/day (maintenance)
Common minor side effects of antithyroid drugs
rash
urticaria
fever
arthralgia (1-5% patients)
Rare but major side effects of antithyroid drugs
hepatitis (propylthiouracil)
cholestasis
vasculitis
AGRANULOCYTOSIS – most important
Selective β1 receptor blocker without sympathomimetic activity which is indicated for THYROID STORM and THYROTOXICOSIS
Propanolol
Used in the early stages before antithyroid drugs take effect
Propanolol
Inhibit the peripheral conversion of T4 to T3 and is used in thyroid storm and Graves ophthalmopathy
Steroids (Dexamethasone, Hydrocortisone, Prednisone)
Used to control TACHYCARDIA in patients with hyperthyroidism whom beta blockers are C.I. (asthma)
Diltiazem
Accelerates T4 breakdown by hepatic enzyme induction
Barbiturates
Lower T4 levels by increasing the fetal excretion of T4
Cholestyramine
Maximum effect of thyroid preparations will be achieved after how many weeks of therapy
6-8 weeks
Methimazole/carbimazole embryopathy
APLASIA CUTIS
CHOANAL ATRESIA
TRACHEOESOPHAGEAL FISTULA
Thyroid Storm
Rare and life-threatening exacerbation of hyperthyroidism
fever, delirium, seizures, coma, vomiting, diarrhea and jaundice
Burch and Wartofsky’s Criteria
> 45 - HIGHLY suggestive of thyroid storm
Precipitants of Thyroid Storm
pre-existing thyrotoxicosis, untreated or partially treated
surgery (poorly prepared patient w/ diffuse toxic goiter for thyroidectomy)
withdrawal of anti-thyroid drug therapy radioiodine therapy vigorous thyroid palpation iodinated contrast dyes salicylates
Laboratory Findings (Thyroid Storm)
Increased FT4 and FT3 Decreased TSH Leukocytosis Mild hypercalcemia (increased bone turnover) Liver function test abnormalities Mild-moderate hyperglycemia
Antithyroid DOC for thyroid storm
PTU - 500 - 1000 mg LD and 250 mg q4h PO or per rectum /per NGT
Primary Hypothyroidism
Iodine deficiency
Autoimmune thyroiditis (Hashimoto’s thyroiditis)
Iatrogenic Hypothyroidism
Subacute Lymphocytic Thyroiditis
Secondary Hypothyroidism
Lesions compressing the pituitary (adenoma, craniopharyngioma, meningioma, empty sella)
Sheehan syndrome
Autoimmune diseases (polyglandular disorders)
Infectious (TB, syphilis)
Symptoms of Hypothyroidism
tiredness, weakness dry skin cold tolerance hair loss difficulty concentrating and poor memory constipation weight gain w/ poor appetite dyspnea hoarse voice menorrhagia paresthesia impaired hearing
Signs of Hypothyroidism
Dry coarse skin Cool Peripheral Extremities Puffy face, hands and feet (myxedema) Diffuse alopecia Bradycardia Peripheral Edema Delayed tendon reflex relaxation Carpal Tunnel Syndrome Serous Cavity Effusions
High TSH, Low FT4
Primary (overt) Hypothyroidism
Autoimmune Hypothyroidism
High TSH, Normal FT4
Mild (subclinical) Hypothyroidism
Early phase treatment of primary hypothyroidism w/ levothyroxine
High TSH, High FT4
TSH producing adenoma
Generalized resistance to thyroid hormone
Preparation of choice for treatment of hypothyroidism
Levothyroxine (LT4)
