29 Questions
What is the first product formed in adrenal steroidogenesis from cholesterol?
Pregnenolone
Which enzyme is responsible for converting cholesterol to pregnenolone in adrenal steroidogenesis?
Cytochrome P450 side chain cleavage enzyme
What is the rate-limiting step for the transport of cholesterol into the inner mitochondrial membrane of the adrenal?
Steroidogenic acute regulatory (StAR) protein function
Where is most of the cholesterol stored in the adrenal gland before stimulation by ACTH?
Cytoplasmic lipid droplets
Which hormone is NOT synthesized in the adrenal cortex?
Epinephrine
What is the main source of cholesterol for the synthesis of adrenal steroid hormones?
Cholesterol esterified and stored in the adrenal
What is the main function of hormones?
To be transported by the circulatory system to act on another tissue
In addition to systemic circulation, where else can hormones act?
On adjacent cells
How can hormones be classified?
By their chemical composition
Which chemical compound is NOT mentioned as being used for synthesizing hormones?
Glucose
Where is most of the precursor for 1,25(OH)2-D3 synthesis produced?
Skin
How are hormones transported to act on other tissues?
Through the circulatory system
Which enzyme complex is responsible for the formation of estradiol from testosterone?
Aromatase
What hormone does the corpus luteum produce and secrete?
Progesterone
What is the major form of vitamin D found in plasma?
25(OH)-D3
From which molecule is 1,25(OH)2-D3 synthesized?
7-dehydrocholesterol
Where are dopamine, norepinephrine, and epinephrine synthesized from tyrosine?
Adrenal medulla
What is the specific binding protein called that most hormones circulate in the blood in bound form to?
Thyroxine-binding globulin (TBG)
Which enzyme deficiencies can cause congenital goiter and often result in hypothyroidism?
DIT deficiency
What primarily controls the activity of the Na+-K+-ATPase-dependent thyroidal I− transporter?
TSH
In the process of hormone synthesis, what is iodinated than glycosylated to form T4 and T3?
Thyroglobulin
What occurs within the thyroglobulin molecule to form T4 or T3?
Coupling of DIT molecules
Where are major amounts of T3 produced even though its synthesis also occurs in the thyroid gland?
Peripheral tissues
What is the more active form of thyroid hormone produced when I− is removed from T4?
T3
Where is insulin synthesized as a preprohormone before being converted to its active form?
Pancreatic beta cells
What is the inactive form of insulin before it undergoes site-specific peptide cleavages?
Pro-insulin
Which enzyme catalyzes the conversion of angiotensinogen precursor to angiotensin I in the Renin-Angiotensin-Aldosterone System?
Renin
Which hormone is released into circulation when blood glucose levels exceed normal ranges?
Insulin
What are the biologically active forms of angiotensin in the Renin-Angiotensin-Aldosterone System?
Ang II and Ang IV
Test your knowledge on the synthesis of steroid hormones and vitamin D, including the conversion of substrates like testosterone and androstenedione, production of progesterone, and activation of 1,25(OH)2-D3.
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