Endocrinology_Thyroid disease_Hypothyroidism Flashcards
Clinical Manifestation of hypothyroidism - Dermatologic
- Decreased blood flow leads to cool skin, coarse hair, and brittle nails.
- Accumulation of glycosaminoglycans in interstitial spaces causes nonpitting edema (myxedema).
Clinical Manifestation of hypothyroidism - cardiovascular
- Decreased heart rate and contractility → decreased cardiac output → dyspnea on exertion.
Clinical Manifestation of hypothyroidism - GIT
- Decreased motility leads to constipation
Clinical Manifestation of hypothyroidism - Hematologic
Normocytic anemia
Clinical Manifestation of hypothyroidism - Reproductive
- Amenorrhea
- menorrhagia
- decreased fertility
Clnical manifestation of hypothyroidism - Neurologic
- Carpal tunnel syndrome and delayed deep tendon reflexes
Clinical manifestation of hypothyroidism - Metabolic
- Increased cholesterol and triglycerides
- decreased free water clearance leads to hyponatremia
- decreased basal metabolic rate → weight gain
What is cretinism?
- Congenital hypothyroidism causing mental retardation and impaired growth
Intepret - Low free T4 and high TSH
- overt hypothyroidism
Intepret - Normal free T4 and high TSH
- subclinical hypothyroidism
Intepret - Low free T4 and low TSH
- Secondary hypothyroidism (rare)
What are some conditions that can cause secondary hypothyroidism?
- pituitary macroadenoma
- Sheehan syndrome, which is a pituitary infarct secondary to postpartum hemorrhage.
What is the most common cause of hypothyroidism?
- Hashimoto thyroiditis, which is a chronic autoimmune thyroiditis.
which auto antibodies mediate destruction of thyroid tissue in Hashimoto thyroiditis?
- antithyroid globulin and anti thyroid peroxidase antibodies.
What are risk factors for developing Hashimoto thyroiditis?
- female gender
- family history of autoimmune disorders.
What are the iatrogenic causes of hypothyroidism?
- thyroidectomy
- external radiation therapy
- radioiodine therapy
Which medications can cause hypothyroidism?
- Lithium
- Amiodarone
- interferon Alpha
- interleukin 2
iodine deficiency can cause hypothyroidism.
True or False?
- True, less than 100 micrograms of iodine per day increases the risk of hypothyroidism
Excess iodine can cause hypothyroidism.
True or False?
- True. Excess iodine can inhibit the organification of T4 and T3.
This is called the Wolff-Chaikoff effect
What percentage of patients with subclinical hypothyroidism progress to overt hyperthyroidism?
- 33% to 55%.
The risk of progression to overt hypothyroidism is associated with higher TSH levels, > 12 and positive antithyroid peroxidase antibodies.
true or false?
True
For patients with subclinical hypothyroidism, under what conditions maythyroid replacement treatment be considered.
- symptomatic patients.
- Patients with TSH >10 - Since treatment appears to prevent progression to overt hypothyroidism
- pregnant patients with TSH more than 4.5 since subclinical hypothyroidism is a risk factor for miscarriage, and low birth weight.
- Patients with goitre since replacement can decrease goiter size.
How do you treat hypothyroidism?
- synthetic L-thyroxine (T4) supplement
How do you measure response to hypothyroidism therapy?
- Check TSH every four to six weeks until euthyroid,
- symptoms can improve, after two weeks.
