Steroid Hormones and Vitamin D Synthesis

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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 Iāˆ’ 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 Iāˆ’ 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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