Which of the following increases LH secretion in males?
A) High testosterone
B) Low testosterone
C) High prolactin
D) High estrogen
📖 شرح: Low testosterone removes negative feedback, increasing LH secretion.
الإجابة الصحيحة: B
Which hormone is released in a pulsatile manner to maintain normal gonadotropin secretion?
A) Oxytocin
B) GnRH
C) ADH
D) Prolactin
📖 شرح: Pulsatile GnRH release is essential for normal FSH and LH secretion.
الإجابة الصحيحة: B
Which organ is the primary site of steroid hormone synthesis?
A) Liver
B) Adrenal gland
C) Pancreas
D) Thyroid gland
📖 شرح: The adrenal cortex is a major site of steroid hormone production.
الإجابة الصحيحة: B
Which precursor molecule is required for all steroid hormones?
A) Tyrosine
B) Cholesterol
C) Glucose
D) Tryptophan
📖 شرح: All steroid hormones are synthesized from cholesterol.
الإجابة الصحيحة: B
Which enzyme converts cholesterol into pregnenolone?
A) Aromatase
B) 21-hydroxylase
C) 17?-hydroxysteroid dehydrogenase
D) Cholesterol desmolase (CYP11A1)
📖 شرح: CYP11A1 catalyzes the rate-limiting step in steroidogenesis.
الإجابة الصحيحة: D
Which hormone stimulates steroid hormone synthesis in the adrenal cortex?
A) TSH
B) ACTH
C) FSH
D) GH
📖 شرح: ACTH stimulates cortisol and androgen synthesis in the adrenal cortex.
الإجابة الصحيحة: B
Which of the following is a mineralocorticoid?
A) Cortisol
B) Aldosterone
C) Testosterone
D) Estradiol
📖 شرح: Aldosterone regulates sodium and water balance.
الإجابة الصحيحة: B
Aromatase converts testosterone into which hormone?
A) Cortisol
B) Progesterone
C) Estradiol
D) Aldosterone
📖 شرح: Aromatase converts androgens into estrogens.
الإجابة الصحيحة: C
Deficiency of 21-hydroxylase leads to which condition?
A) Hypothyroidism
B) Congenital adrenal hyperplasia
C) Diabetes mellitus
D) Cushing syndrome
📖 شرح: 21-hydroxylase deficiency impairs cortisol and aldosterone synthesis.
الإجابة الصحيحة: B
Which steroid hormone is primarily produced in the zona glomerulosa?
A) Cortisol
B) Aldosterone
C) DHEA
D) Testosterone
📖 شرح: The zona glomerulosa synthesizes mineralocorticoids.
الإجابة الصحيحة: B
Which of the following increases steroid hormone synthesis?
A) Increased cholesterol availability
B) Decreased ACTH
C) Low LDL uptake
D) Inhibition of CYP enzymes
📖 شرح: Cholesterol is the essential substrate for steroidogenesis.
الإجابة الصحيحة: A
Which hormone is synthesized in the zona fasciculata?
A) Aldosterone
B) Cortisol
C) Estradiol
D) Progesterone
📖 شرح: The zona fasciculata is responsible for glucocorticoid production.
الإجابة الصحيحة: B
Which receptor type do steroid hormones primarily bind to?
A) Cell surface receptors
B) Nuclear receptors
C) G-protein coupled receptors
D) Ion channel receptors
📖 شرح: Steroid hormones bind intracellular nuclear receptors to regulate gene transcription.
الإجابة الصحيحة: B
Where are steroid hormone receptors typically located?
A) On the plasma membrane
B) In the cytoplasm or nucleus
C) In the mitochondria
D) In the Golgi apparatus
📖 شرح: Steroid receptors are intracellular and translocate to the nucleus after activation.
الإجابة الصحيحة: B
What is the primary mechanism of action of steroid hormones?
A) Activation of second messengers
B) Direct regulation of gene transcription
C) Opening of ion channels
D) Protein phosphorylation
📖 شرح: Steroid hormones alter gene expression by binding DNA response elements.
الإجابة الصحيحة: B
Which enzyme is responsible for converting cortisol into cortisone?
A) 11?-hydroxylase
B) Aromatase
C) 11?-HSD2
D) 5?-reductase
📖 شرح: 11?-HSD2 inactivates cortisol by converting it to cortisone.
الإجابة الصحيحة: C
Which organ is the major site of steroid hormone metabolism?
A) Kidney
B) Liver
C) Pancreas
D) Thyroid
📖 شرح: The liver metabolizes steroid hormones for excretion.
الإجابة الصحيحة: B
Steroid hormones are transported in blood primarily bound to:
A) Albumin and specific binding globulins
B) Free in plasma
C) Hemoglobin
D) Platelets
📖 شرح: Steroid hormones circulate bound to SHBG, CBG, and albumin.
الإجابة الصحيحة: A
Which hormone requires 5?-reductase for conversion to its active form?
A) Estradiol
B) Cortisol
C) Dihydrotestosterone (DHT)
D) Aldosterone
📖 شرح: Testosterone is converted to DHT by 5?-reductase.
الإجابة الصحيحة: C
Which factor increases steroid hormone half-life?
A) Being water-soluble
B) Binding to plasma proteins
C) Rapid hepatic metabolism
D) Renal filtration
📖 شرح: Protein binding protects steroid hormones from rapid clearance.
الإجابة الصحيحة: B