I  just read an  old   post (here) on hiding your adams apple-  and  wanted to  comment.
One  can  detect    "A male to female transsexual"    by her  adams apple.
from  Wikipedia
The dam's apple (technically known as the laryngeal prominence) is a feature of the human neck and refers to the lump or protrusion that is formed by the angle of the thyroid cartilage surrounding the larynx.
The structure of the laryngeal prominence forms a bump under the skin. It is larger in adult men, in whom it is usually clearly visible and palpable. In women, the bump is much less visible and is hardly perceived on the upper edge of the thyroid cartilage.[1]
The meeting point of the two portions of the cartilage generally forms an acute angle (of about 90°) in men, while in women, an open arc (of about 120°).
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Although both sexes have it, Adam's apple is considered a characteristic feature of adult men, because its size tends to increase considerably during puberty.[8]
Its development is considered a secondary sexual characteristic of males, that appears as a result of hormonal activity. Its level of development varies from individual and the widening of that area in the larynx can occur very suddenly and quickly.
The Adam's apple, in conjunction with the thyroid cartilage which forms it, helps to protect the walls and the frontal part of the larynx, including the vocal chords (which are located directly behind it).
Another function of the laryngeal protuberance is related to the deepening of the voice. During adolescence, the thyroid cartilage grows together with the larynx. Consequently, the laryngeal protrusion grows in size mainly in men. Together, a larger soundboard is made up in phonation apparatus, and, as a result, the man gets a deeper tone
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Testosterone in a male  causes  two things  to occur  at the same  time?  a   large  protruding  adams  apple  and a  masculine voice-  correlation  doesn't prove  causation  -  but  maybe  they are  related?    
That indicates  to me  that if one were to  push his thumb  directly on the  adams  apple  for a few  minutes  at  a  time  over a period of  a  few  days,  the  cartilage  supporting  it    would  form hairline  tears,  as  the  adams  apple  moved  toward   the  rear  of the throat.  the adams  apple  would  stay  in its  new  position  , after the  cartilage  healed.   That would  change the  tension of the vocal cords    and  shape of the voice box- probably  creating a more feminine voice??
a  more  detailed  study of  the  structure  would  indicate  the  outcome.
isabella