5 alpha reductase defiency

[anbuitachi]

First aid says there is ambiguous external genitalia, until puberty, for males w/ 5a reductase deficiency [page 513]. Why is it until puberty? What happens at puberty that removes this deficiency?

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[CrouchingLiger]

There still is that deficiency after puberty. However, also at puberty, the levels of testosterone increase dramatically. Testosterone can activate those same receptors that DHT acts at if it is at a high enough concentration. So, in these cases, the testosterone levels are much higher (because there is no negative feedback via DHT to shut down LH), leading to similar sexual development because it can then act like DHT.

 

[startswithb]

Increased testosterone causes growth of external genitalia.

 

[MDSlacker]

The actual reason is that there are two types of 5 alpha reductase enzymes. At puberty the second type is upregulated as well as the amount of testosterone and therefore you actually have an increase in DHT and therefore get secondary sexual characteristics.

 

[anbuitachi]

Thanks!!!

 

[MLT2MT2DO]

The actual reason is that there are two types of 5 alpha reductase enzymes. At puberty the second type is upregulated as well as the amount of testosterone and therefore you actually have an increase in DHT and therefore get secondary sexual characteristics.

Do you have a reference for this?

 

[MDSlacker]

Do you have a reference for this?

I had a UWorld Question on it. The question ID is 0954 for anyone that wants to look it up. And I actually had it backwards, type 2 is the one that is present at birth and is found in the skin and this is the one that is defective in 5-alpha reductase deficiency. At puberty the type 1 receptor is upregulated which is found in the genitals and this is responsible for the secondary sex characteristics seen at puberty.

 

[DrPettans]

There still is that deficiency after puberty. However, also at puberty, the levels of testosterone increase dramatically. Testosterone can activate those same receptors that DHT acts at if it is at a high enough concentration. So, in these cases, the testosterone levels are much higher (because there is no negative feedback via DHT to shut down LH), leading to similar sexual development because it can then act like DHT.

But high testosterone would also inhibit LH secretion, by negative feed back. Why is Testosterone high then?