Precocious and delayed puberty, amenorrhea, and PCOS with their underlying hormonal mechanisms tested on USMLE Step 1.
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- Precocious puberty in girls is generally defined as onset before age
- 8 years
- Precocious puberty in boys is generally defined as onset before age
- 9 years
- Central (GnRH-dependent) precocious puberty results from
- Early activation of the hypothalamic-pituitary-gonadal axis
- Peripheral (GnRH-independent) precocious puberty results from
- A source of sex hormone outside of normal hypothalamic-pituitary-gonadal axis activation, such as an ovarian or adrenal tumor
- The typical order of pubertal changes in girls (Tanner sequence)
- Thelarche (breast development), then pubarche (pubic hair), then menarche
- Thelarche refers to
- The onset of breast development
- Menarche refers to
- The first menstrual period
- Delayed puberty in girls is generally defined as absence of breast development by age
- 13 years
- Primary amenorrhea is defined as
- Absence of menarche by age 15 in the presence of normal secondary sexual characteristics
- Secondary amenorrhea is defined as
- Absence of menstrual periods for 3 or more months in a woman who previously menstruated
- The most common cause of secondary amenorrhea to exclude first
- Pregnancy
- Turner syndrome as a cause of primary amenorrhea presents with
- Streak ovaries and absent secondary sexual characteristics due to gonadal dysgenesis
- Mullerian agenesis (Mayer-Rokitansky-Kuster-Hauser syndrome) causes primary amenorrhea by
- Absent or underdeveloped uterus and upper vagina despite normal ovarian function
- Functional hypothalamic amenorrhea is commonly caused by
- Excessive exercise, low body weight, or significant psychological stress
- Asherman syndrome causes secondary amenorrhea through
- Intrauterine adhesions, often following uterine instrumentation such as dilation and curettage
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