Chapter 40: Disorders of Endocrine Function Flashcards Preview

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Flashcards in Chapter 40: Disorders of Endocrine Function Deck (13):

Thyroid Hormone Disorders

- Thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are regulated by thyroid-stimulating hormone (TSH) secretion from the anterior pituitary

- Thyroid hormones produced in follicular cells of thyroid (Regulators of metabolism; required for normal growth and development of tissues)



- May be congenital or acquired

- Majority are primary, due to intrinsic thyroid gland dysfunction

- Congenital hypothyroidism (cretinism) typically due to thyroid dysgenesis (lack of development)

- Secondary, due to defects in TSH production (hyposecretion) usually associated with head/brain conditions

- Most common cause of acquired hypothyroidism: lymphocytic thyroiditis (Hashimoto or autoimmune thyroiditis)

- Irradiation of the thyroid gland

- Surgical removal of thyroid tissue

- Iodine deficiency (required for T3, T4 formation) (Leads to lack of T3/T4, stimulates TSH secretion) (Increased TSH causes thyroid cells to secrete large amounts of thyroglobulin, which leads to goiter)


Hypothyroidism: Clinical manifestaitons in infants

- Routine screening in newborns has resulted in increased treatment for congenital hypothyroidism

- Dull appearance, thick, protuberant tongue, and thick lips

- Prolonged neonatal jaundice

- Poor muscle tone, umbilical hernia

- Bradycardia, mottled extremities

- Hoarse cry

- Mental retardation unless treated early


Hypothyroidism: Clinical manifestations in children/adults

- Decreased basal metabolic rate

- Weakness, lethargy, cold intolerance, decreased appetite

- Bradycardia, narrowed pulse pressure, and mild/moderate weight gain

- Elevated serum cholesterol and triglycerides

- Enlarged thyroid, dry skin, constipation

-Depression, difficulties with concentration/memory

-Loss of eyebrow

- Menstrual irregularity


Diagnosis of Hypothyroidism

- Primary: elevated TSH (sensitive indicator of thyroid hypoactivity)

- Secondary: low TSH

- Low levels of T3 and T4 may not occur until later in the disease course


Treatment of Hypothyroidism

- Goal is return of euthyroid (normal) state

- Must progress slowly

- Oral levothyroxine

- Resolution of symptoms occurs over weeks


Hypothyroidism (Myxedema)

- occurs in sever or prolonged hypothyroidism

- Generalized, non-pitting edema

- Decreased level of consciousness, hypotension, hypothermia, history of precipitating event (trauma, sepsis, certain drugs)

- May progress to myxedema coma, a life-threatening condition if treatment not received


Pathogenesis of Hyperthyroidism

- Most common: autoantibodies bind and stimulate TSH receptors leading to diffuse toxic goiter (Graves disease)

- Associated with certain genetic markers

- Thyromegaly

- Exophthalmos (immune mediated so may not resolve with treatment)

- Widening of the palpebral fissure resulting in exposed sclera

- Lid lag, vision changes, photophobia


Etiology of Hyperthyroidism

- Thyroid hyperfunction with increased synthesis and secretion of T4 and T3 (Graves disease)

- Thyroid destruction with release of preformed T4 and T3 (Hashimoto thyroiditis)

- Primary—Graves disease, autoimmune, tumor related, inflammatory (Autoimmune—related to TSH receptor antibodies)

- Secondary—stimulation of TSH receptors by TSH (hypersecretion of TSH)


Clinical Manifestations of Hyperthyroidism

- Changes in behavior, insomnia, restlessness, tremor, irritability, palpitations, heat intolerance, diaphoresis, diarrhea, inability to concentrate that interferes with work performance; enlarged thyroid gland

- Increased basal metabolic rate leads to weight loss, although appetite and dietary intake increase

- Amenorrhea/scant menses


Diagnosis of Hyperthyroidism

- TSH levels (TSH helpful in differentiating primary (low TSH) from secondary (high TSH) hyperthyroidism)

- Elevated serum T4 and T3 (confirm)

- 24-hour radioactive iodine uptake study can confirm diagnosis of Graves disease and exclude presence of thyroid neoplasms


Treatment of Hyperthyroidism

- Beta-blockers to block acute symptoms

- Antithyroid drugs, thionamides (propylthiouracil, methimazole)

- Radioactive iodine treatment (destroys part of thyroid for Graves disease)

- Surgical removal of the thyroid gland typically reserved for tumors

- Pituitary adenoma treated surgically


Hyperthyroidism (Thyroid Storm)

- Life-threatening thyrotoxicosis that occurs when excessive amounts of thyroid hormones are acutely released into circulation

- Clinical Manifestations include Elevated temperatures, tachycardia, arrhythmias, congestive heart failure, Extreme restlessness, agitation, and psychosis (Precipitating event: stress, gland manipulation)

- Treatment includes Aggressive management to achieve metabolic balance,
Antithyroid drugs are given followed by iodine administration, Beta-blockers to alleviate cardiac symptoms,
Antipyretic therapy, Fluid replacement, Surgical removal of tumors, Fatal if not treated