Uworld13 Flashcards
Function of aromatase and its deficiency
Aromatase is responsible for converting androgens into estrogens.
Deficiency of this enzyme causes accumulation of androgens during pregnancy, resulting in ambiguous external genitalia in newborn females and maternal gestational virilization
What is stranger anxiety?
Stranger anxiety, which presents as crying or screaming when unfamiliar people approach, is a normal and expected part of childhood development.
It typically begins around 6 months and resolves by 2 years.
What is thyroid hormone resistance?
Decreased sensitivity of peripheral tissues to thyroid hormones due to a defect in the thyroid hormone receptor.
Levels of thyroxine, triiodothyronine, and TSH are increased.
Patients classically have goiter and frequently develop attention deficit hyperactivity disorder.
What is lateral epicondylitis (tennis elbow)?
Overuse of wrist extensor muscles (extensor carpi radialis, extensor digitorum) leading to angiofibroblastic tendinitis at their attachment on the lateral epicondyle
Unlike Plasmodium falciparum, the eradication of Plasmodium vivax and Plasmodium ovale requires?
Requires primaquine to target the dormant hepatic phase.
Patients not receiving treatment that targets the hepatic phase will likely develop relapsed symptoms weeks or months later.
The work of breathing is minimized in patients with?
Increased elastic resistance (eg pulmonary fibrosis) when their respiratory rate is high and tidal volume is low (fast, shallow breaths)
What is the work of breathing in patients with diseases that increase airflow resistance (eg, asthma, chronic obstructive pulmonary disease)?
Breathe at a lower respiratory rate and higher tidal volume (slow, deep breathes) to minimize the work of breathing.
Treatment for bulimia nervosa?
Nutritional rehabilitation, cognitive-behavioral therapy, and pharmacotherapy with selective serotonin reuptake inhibitors. Fluoxetine is drug of choice.
What is ataxia-telangiectasia?
AR; results from a defect in DNA-repair genes.
The DNA of these patients is hypersensitive to ionizing radiation.
Manifestations include cerebellar ataxia, oculocutaneous telangiectasias, repeated sinopulmonary infections, and an increased incidence of malignancy.
What is the function of neprilysin?
Neprolysin is responsible for the breakdown of the natriuretic peptides and angiotensin II; therefore, inhibition of neprilysin increases the activity of these peptides.
For treatment of heart failure, neprilysin inhibition is combined with angiotensin II receptor blockade to optimize the positive effects of the natriuretic peptides (vasodilation, diuresis) while blocking the negative effects of angiotensin II (eg vasocontriction, fluid retention)
Pelvic fracture are frequently associated with injury to?
The posterior urethra, in particular the bulbomembranous junction.
Inability to void despite a full bladder sensation, a high riding boddy prostate, and blood at the urethral meatus are clinical findings suggestive of urethral injury.
How do penicillins and cephalosporins function?
By irreversibly binding to penicillin-binding proteins such as transpeptidases.
A change in the structure of penicillin-binding proteins that prevents cephalosporin binding is one mechanism of bacterial resistance to cephalosporins.
What are the potassium levels in diabetic ketoacidosis?
Most patients with diabetic ketoacidosis have normal to increased serum potassium levels despite a total body potassium deficit.
Replacement of potassium is a crucial step in the management of patients with diabetic ketoacidosis.
MOA of letrozole
Polycystic ovary syndrome can present with irregular menses, enlarged ovaries, and anovulatory infertility.
Letrozole, an aromatase inhibitor, acts on the ovary and peripheral adipose tissue to inhibit androgen-to-estrogen conversion by the enzyme aromatase; the subsequent decrease in estrogen production causes the pituitary to release more FSH and LH, thereby stimulating ovulation
Where do potassium sparing diuretics (spironolactone, amiloride) act on the nephron?
Act on the late distal tubule and cortical collecting duct to antagonize the effects of aldosterone
All diuretics except the potassium sparing class cause potassium loss by increasing sodium delivery to the late distal tubule and cortical collecting duct, where aldosterone-induced sodium reabsorption occurs at the expense of potassium.
What is the path of the phosphoinositol second messenger system?
The phosphoinositol second messenger system begins with ligand-receptor binding and Gq protein activation leading to activation of phospholipase C (PLC).
PLC then hydrolyzes phosphatidyl inositol bisphosphate and forms diacylglycerol and inositol triphosphate (IP3)
Finally, IP3 activated protein kinase C via an increase in intracellular Ca2+
Central nervous system lesions cause what to the face?
Because the upper face receives bilateral input from the motor cortices, central nervous system lesions typically cause lower facial weakness that spares the forehead on one side of the fact.
Peripheral lesions (Bell palsy) cause what to the face?
cause weakness of the entire side of the face. Bell palsy may also result in decreased tear production, hyperacusis, and reduced taste sensation.
How can SNRI be used for neuropathic pain?
Serotonin-norepinephrine reuptake inhibitors are often used for neuropathic pain. They increase norepinephrine in the central synapses, which modulates the descending pain pathway, leading to decreased central perception of pain.
What is primary ciliary dyskinesia?
results from an autosomal recessive mutation in the proteins responsible for normal flagellar and ciliary structure and function (eg, dynein, assembly proteins)
CF: situs inversus, chronic sinusitis, bronchiectasis, and infertility.
What is the most life threatening complication associated with Marfan syndrome?
Cardiovascular lesions.
Early onset cystic medial degeneration of the aorta predisposes to aortic dissection, the most common cause of death in these patients.
When should Turner syndrome be suspected?
Turner syndrome (loss of an X chromosome) should be suspected in a newborn girl with cystic hygroma or lymphedema.
Dysmorphic features (high arched palate, low set ears) and aortic anomalies (coarctation) are some findings.
What is a harmartoma?
Hamartomas are common, slow growing, benign lung neoplasms microscopically characterized by nodules of disorganized, mature connective tissue (cartilage, fat) and entrapped respiratory epithelium. They are often detected incidentally by imaging, appearing as well circumscribed, peripheral, solitary lung lesions.
Lymph from the testes drains?
Through lymph channels directly back to the para-aortic lymph nodes