FMPP

Familial male-limited precocious puberty (FMPP), Familial Sexual Precocity, or Gonadotropin-independent Testotoxicosis is an intersex condition that effects AMAB and/or CTM people. It is unknown how common it is, however it is rare.

Those with this condition hit an early puberty, beggining sexual development at the ages of 2-5. This may cause a lot of confusion within the child, as their mind is not yet developed to understand these changes within their body.

The changes include body hair, acne, a deepening voice, spontaneous erections, penile growth, sexual desire/interest at an early age (unless they are ace-spec,) and increased height. Those with this condition tend to stop growing at a very early age, due to their early puberty, and tend to be shorter than the rest of their family.

Those with this condition also have CTM hyperandrogenism.

Causes
This condition is caused by mutations in the LHCGR gene. The LHCGR gene provides instructions for proteins that luteinize the hormone/chorionic gonadotropin receptor, which is what causes a stable development in androgens and other horomones.

Because of this gene mutation, horomonal activity tends to begin early and at an increased rate, causing the individual to grow masculine traits at an early age.

Resources

 * https://medlineplus.gov/genetics/condition/familial-male-limited-precocious-puberty/
 * https://journals.lww.com/theendocrinologist/Abstract/2004/05000/Familial_Male_Limited_Precocious_Puberty.9.aspx
 * https://en.wikipedia.org/wiki/Familial_male-limited_precocious_puberty