Week 11: Chp 43: Hypothyroidism Flashcards
The release of thyroid hormone is under the control of what?
-the anterior pituitary gland (secretion of TSH) and
-the hypothalamus (secretion of TRH)
>disorders affecting either of these structures can result in hypothyroidism
Hypothyroidism is largely associated with what?
-autoimmune disease, thyroid surgery, or radioactive iodine therapy used in the treatment of hyperthyroidism
What is the most common type of hypothyroidism?
Hashimoto’s thyroiditis
-caused by an autoimmune response that leads to destruction of the thyroid gland by immunological processes
Hashimoto’s Thyroiditis
caused by an autoimmune response that leads to destruction of the thyroid gland by immunological processes
-most common type of hypothyroidism
Hypothyroidism can also be associated with what deficiencies?
iodine and tyrosine deficiencies
-because they are needed for the synthesis of thyroid hormone, but rarely observed in US because of the use of iodized salt
Other causes of Hypothroidism
congenital thyroid disorders, autoimmune thyroid destruction, and thyroid cancer
Hypothyroidism is a major cause of what?
Goiter (enlargement of the thyroid gland)
-and develops secondary to thyroid gland hypertrophy in an attempt to produce normal amounts of T3 and T4
Hypothyroidism occurs most often in who?
in women between the ages of 30 and 60 and incidence increases with age
What is the hallmark of hypothroidism?
decreased metabolism
-affects most body systems
Primary Vs Secondary Vs Tertiary Hypothyroidism
- Primary; develops as a result of a disorder of the thyroid itself
- Secondary; is caused by a disorder of the anterior pituitary gland
- Tertiary: due to a disorder of the hypothalamus; lack of TRH from the hypothalamus
The hypometabolic state is characterized by what manifestations?
- decreased energy
- increased sleep
- fatigue
- weight gain
- decreased appetite
- susceptibility to cold temperatures
Patients with hypothyroidism may develop what condition?
myxedema
-a condition resulting from an increased deposition of glycosaminoglycans (a type of polysaccharide) in cells and tissues
Myxedema; The increased deposition of glycosaminoglycans causes what?
- an osmotic edema and fluid collection that is associated with a generalized non-pitting edema
- cardiac alterations secondary to myxedematous changes include decreased contractility, cardiac enlargement, pericardial effusion, decreased pulse, and decreased cardiac output
- decreased gastrointestinal activity results in constipation and abdominal distension
- skin changes may result over time secondary to cold intolerance, and a lack of sweating may leave the skin dry and coarse
- hair becomes thin and fragile, and hair loss occurs
Myxedema related to hypothyroidism, how a patient presents
- facial puffiness
- hair dry, coarse, thin, and fragile
- lateral eyebrows thin
- periorbital edema (bags under eyes)
- skin dry and coarse due to lack of sweating
The diagnosis of hypothyroidism can be confirmed through what?
analysis of laboratory data, including T3, T4, and TSH
- if the etiology is primary hypothyroidism, the TSH level is elevated as a result of the feedback system to the hypothalamus and anterior pituitary gland caused by low circulating levels of thyroid hormones (T3 and T4)
- In secondary or tertiary, the TSH may be high or near normal because the disorder is a result of pathophysiology in the anterior pituitary gland or hypothalamus
- When Hashimoto’s thyroiditis is suspected, an evaluation of anti-thyroid antibodies should be performed
Laboratory Tests for thyroid disorders
- Free T3 (triiodothyronine)
- Total T3 (triiodothyronine)
- Free T4 (thyroxine)
- Total T4 (thyroxine)
- TSH (thyroid-stimulating hormone)
Thyroid Disorders Lab tests: Free T3
Normal Range: 2.6- 4.8 pg/mL
Significance: decreased in hypothyroidism; increased in hyperthyroidism
Thyroid Disorder Lab Tests: Total T3
Normal Range: 70 to 204 ng/dL
Significance: Decreased in hypothyroidism, Increased in hyperthyroidism