Question

Which one of the following correctly describes the mode of action of Follicle Stimulating Hormone (FSH) and estrogen?

• A. FSH interacts with membrane-bound receptor and generates cyclic AMP, while estrogen interacts with intracellular receptor and regulates gene expression
• B. FSH interacts with intracellular receptor and generates cyclic AMP, while estrogen interacts with membrane-bound receptor and regulates cellular metabolism
• C. Both FSH and estrogen regulate gene expression via intracellular receptors
• D. Both FSH and estrogen regulate cellular metabolism via membrane-bound receptors

Hint:

Protein/Peptide Hormones (FSH, LH, Insulin, Glucagon) = Membrane receptors + Second messenger (cAMP, $IP_3$, $Ca^{2+}$).
Steroid/Thyroid Hormones (Estrogen, Progesterone, Testosterone, Thyroxine) = Intracellular/Nuclear receptors + Direct Gene Regulation.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Hormones are classified by their chemical nature, which determines their mechanism of action (signal transduction).

Step 2: Detailed Explanation:
$\bullet$ FSH (Follicle Stimulating Hormone): This is a protein/peptide hormone. Protein hormones are large and hydrophilic; they cannot cross the lipid bilayer of the cell membrane. They bind to extracellular receptors (membrane-bound) and trigger second messengers like cyclic AMP (cAMP) to relay the signal.
$\bullet$ Estrogen: This is a steroid hormone derived from cholesterol. Steroid hormones are lipophilic and can easily diffuse through the plasma membrane. They bind to intracellular receptors (cytoplasmic or nuclear). The hormone-receptor complex then binds to DNA to directly regulate gene expression.

Step 3: Final Answer:
FSH uses membrane receptors/cAMP, and estrogen uses intracellular receptors/gene regulation.
This matches option (A).