Question
A 16-year-old girl is brought to the clinic by her mother with concerns regarding the lack of any signs of puberty. The appearance of external genitalia is of a normal prepubertal female. Laboratory studies show markedly elevated FSH and LH levels. Which of the following causes of delayed puberty accompanies elevated circulating gonadotropin levels?
| A. |
chronic illness
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| B. |
gonadal dysgenesis
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| C. |
hypothalamic tumors
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| D. |
Kallmann syndrome
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Show Answer
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Correct Answer � B
Explanation
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Ans. . (B)
- Puberty is delayed when secondary sex development fails to occur by 13 years of age in girls or 14 years in boys.
- Low circulating sex steroid levels delay epiphyseal closure, leading to prolonged growth of extremities.
- Delayed puberty results from the absence of either gonadal or hypothalamic-pituitary function.
- Absence of gonadal function due to defective gonadal development (gonadal dysgenesis) leads to a rise in circulating gonadotropin levels (hyper-gonadotropic hypogonadism) because negative feedback restraint is removed from the hypothalamus and pituitary.
- Moreover, the absence of pulsatile GnRH due to hypothalamic suppression causes a decline in circulating gonadotropin levels (hypogonadotropic hypogonadism).
- Suppression of hypothalamic GnRH may reflect the presence of central nervous system(CNS) tumors and diseases, malnutrition, chronic illness, or stress. Kallmann syndrome refers to GnRH deficiency, combined with anosmia due to olfactory bulb agenesis.
- This syndrome may be due to a defect in the migration of GnRH-containing neurons from the nasal placode to the hypothalamus.
