Repeated USMLE Questions Step 1- Review- 1

Q- Thyroid hormone can cause which one of the following effects?

A- Hypoglycemia

B- Lowers blood cholesterol

C- Lowers body temperature

D- Lowers oxygen consumption

B- Lowers blood cholesterol- Thyroid hormone act on the nucleus and altering the rate of gene expression. It causes increase in oxygen consumption, decreased blood cholesterol levels, hyperglycemia and thermogenesis.

Q- Which one of the following enzymes is associated with Lyesh-Nyhan syndrome?

A- Adenosine deaminase

B- Hypoxanthine-guanine phosphoribosyl transferase

C- Ribonucleotide reductase

D- Xanthine oxidase

B- Hypoxanthine-guanine phosphoribosyl transferase- This enzyme is a part of the salvage pathway for purines. A deficiency leads to inability to recycle purines which results in overproduction of uric acid. Individuals with Lesch-Nyhan syndrome are mentally retarded. 

Q- Pemphigus is an autoimmune skin disease associated with which of the following structures? ,

A- Cell matrix junctions

B- Desmosomes

C- Gap junctions

D- Tight junctions

B- Desmosomes- Pemphigus is caused by autoantibodies against the transmembrane glycoproteins. These antibodies bind to proteins and disrupt the desmosomes.

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