The extraordinary case of the Guevedoces - Deepstash
The extraordinary case of the Guevedoces

The extraordinary case of the Guevedoces

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The extraordinary case of the Guevedoces

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MICHAEL MOSLEY

The discovery of a small community in the Dominican Republic, where some males are born looking like girls and only grow penises at puberty, has led to the development of a blockbuster drug that has helped millions of people

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To Understand How, We Need A Lesson On Human Sex Differentiation

  1. Humans have an XY sex-determination system.
  2. The Y chromosome carries the SRY gene (also known as TDF) which determines testicular formation.
  3. The testes formed in the presence of the SRY gene secretes hormones (dihydro-testosterone).
  4. Hormonal changes induce development of external & internal sex organs (penis, scrotum & wolffian ducts).
  5. The absence of SRY gene leads to the development of different internal and external organs (vulva, uterus, fallopian tubes).

This process of sex organ development through chromosomal & hormonal mechanisms is known as sex differentiation.

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Biological Processes Are Never Universal

The process of sex differentiation ensures that human fetuses are born with distinct external & internal genitalia (which is used to assign their sex at birth).

However, in a small town in the Dominican Republic, a community known as the "Guevedoces" (translating to "penis at twelve") undergo a different process of sex differentiation.

Many of them are brought up girls due to the absence a penis & testes & the presence of a vagina.

When puberty approaches, some of their male sexual organs grow, and their biological sex is reassigned as male according to their genitalia.

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So why does it happen?

In the 1970s, Dr Julianne Imperato-McGinley, discovered that they have a genetic condition that causes a deficiency in an enzyme called 5-alpha-reductase, which converts testosterone into dihydro-testosterone.

Thus, male external & internal genitalia do not develop despite the presence of the Y chromosome & SRY gene, and they appear female when they are born.

At puberty, a surge of testosterone causes their body to develop internal & external male genitalia alongside secondary male characteristics.

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How Did The Guevedocs Helped Develop A Drug That Helps Millions?

Another thing that Imperato-McGinley discovered was that the Guevedoces tend to have small prostates.

This observation led to the development of the best-selling drug, finasteride, which blocks the action of 5-alpha-reductase, mimicking the lack of dihydro-testosterone seen in the Guevedoces.

Finasteride is an effective way to treat Benign prostate hyperplasia & male pattern baldness, hirsutism in women & is part of hormone therapy for transgender woman.

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What Do These Findings Imply On Human Sexuality?

A final interesting observation that Imperato-McGinley made was that these boys, despite being brought up as girls, almost all showed strong heterosexual preferences. She concluded prenatal hormones play a bigger role in the development of sexual orientation compared to external influences.

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