Intracellular receptors

Consider these hormones:

I. Cortisol
II. Vitamin D
III. Epinephrine
IV. T3

Which ones have intracellular receptors?

A. I and III

B. I and IV

C. II and III

D. II and IV

E. III and IV

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it’s not an option but i’d say cortisol and vitamin D derive from cholesterol so they should be lipophilic, pass through the membrane, then be shuttled to a nucleus receptor or to an cytoplasmic receptor
What is the answer to this question?

The answer is D, 2& 4 only.


I also first thought I and II should have intracellular receptors, but I have checked that cortisol is actually very polar (although a steroid), so it cannot pass directly through cell membrane. Cortisol = alcohol (polar)

We must remember that only completely non-polar hormones can enter the cell and bind to their intracellular receptors inside the cell. Other hormones act through second messenger and only have extracellular receptors:)


Although T3 being an Amine hormone is exception and can cross the membrane to bind to Intracellular receptors is this reasoning correct?
I was thinking of I II and IV but that was not even a option HAHA.


Hey! Yes thats correct, remember that amino acid derivatives like T3 can act as either peptide hormones (polar) or steroid hormones (usually non-polar, but we see an exception in the polar cortisol)


Other than T3, what exceptions do we have to remember? (The exceptions which can be either hydrophobic or hydrophilic )

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For example, adrenaline, noradrenaline and thyroxine = all are amino acid derivatives and very polar so act through second messenger.

Most peptide hormones act through second messenger due to their polarity as well.

Most steroid hormones are nonpolar and pass directly through phospholipid bilayer in the cell, therefore do not need second messenger. Exceptions are those with ending -ol (alcohols like cortis-ol)