A 15-year-old boy is brought to the office due to concern about puberty being delayed. He is the shortest boy in his class and his voice has not started to change. The patient is otherwise well and has no headaches, vision changes, or vomiting. He is an average student in high school and a member of the cross-country team. He eats a well-balanced diet and has a good energy level. The patient has allergic rhinitis, for which he takes loratadine. He takes no other medications, and his vaccinations are up to date. His mother underwent menarche at age 13 and his father had facial hair at age 14. Vital signs are normal. The patient's growth chart is shown in the exhibit. On physical examination, he appears well nourished. Cranial nerves II-XII are intact, and there are no focal deficits. Visual fields are full to confrontation. There is no facial hair or acne. The neck is supple with no masses. Cardiopulmonary examination is normal. The abdomen is soft and nondistended without palpable masses. The genital area has no pubic hair. The testes are symmetric and small, measuring 2.5 cm in length and 2 mL in volume. A bone age radiograph is consistent with age 13 years, 2 months. Which of the following is the best next step in management of this patient?
A)FSH, LH, and testosterone levels
B)GnRH stimulation test
C)Karyotype analysis
D)MRI of the brain
E)Reassurance and follow-up in 6 months

Question

A 15-year-old boy is brought to the office due to concern about puberty being delayed.  He is the shortest boy in his class and his voice has not started to change.  The patient is otherwise well and has no headaches, vision changes, or vomiting.  He is an average student in high school and a member of the cross-country team.  He eats a well-balanced diet and has a good energy level.  The patient has allergic rhinitis, for which he takes loratadine.  He takes no other medications, and his vaccinations are up to date.  His mother underwent menarche at age 13 and his father had facial hair at age 14.  Vital signs are normal.  The patient's growth chart is shown in the exhibit.  On physical examination, he appears well nourished.  Cranial nerves II-XII are intact, and there are no focal deficits.  Visual fields are full to confrontation.  There is no facial hair or acne.  The neck is supple with no masses.  Cardiopulmonary examination is normal.  The abdomen is soft and nondistended without palpable masses.  The genital area has no pubic hair.  The testes are symmetric and small, measuring 2.5 cm in length and 2 mL in volume.  A bone age radiograph is consistent with age 13 years, 2 months.  Which of the following is the best next step in management of this patient?
A)FSH, LH, and testosterone levels 
B)GnRH stimulation test 
C)Karyotype analysis 
D)MRI of the brain 
E)Reassurance and follow-up in 6 months

Quizplus · Accepted Answer

Explanation: 11ec2b69_c131_cf04_8f63_b317f73376e7_MD0005_00 Delayed puberty in boys is defined as lack of testicular enlargement (>4 mL) by age 14 and is due to the inadequate secretion of testosterone required for normal pubertal development. Hypogonadism may be classified as primary due to gonadal failure or, more commonly, secondary due to impaired GnRH (hypogonadotropic hypogonadism). normal pubertal development The most common cause of delayed puberty and hypogonadism is constitutional delay. Late maturation of the hypothalamic-pituitary-gonadal axis results in a delayed bone age and short stature (<3rd percentile) but normal growth velocity. Other causes of hypogonadotropic hypogonadism may be functional (eg, chronic illness, malnutrition, stress), genetic (eg, Kallmann syndrome), or due to hypothalamic/pituitary pathology (eg, craniopharyngioma). This adolescent is showing signs of hypogonadism, including prepubertal testes and absent facial and pubic hair. He is also below average height due to a delayed pubertal growth spurt. A bone age radiograph is indicated to assess remaining growth potential and, although delayed, he does not have short stature or a family history of "late bloomers" as expected with constitutional delay. Therefore, further testing to exclude pathologic etiologies is necessary (Choice E). Initial evaluation includes FSH, LH, and testosterone levels to differentiate between primary (elevated FSH/LH) and secondary (low to normal FSH/LH) hypogonadism. Prolactin and TSH tests should also be ordered, as increased levels interfere with GnRH secretion. (Choice B) Although GnRH stimulation increases FSH/LH in patients with secondary hypogonadism, it cannot differentiate constitutional delay from other causes of GnRH deficiency and is not recommended for evaluating pubertal delay. (Choice C) If initial laboratory testing is concerning for primary hypogonadism, a karyotype is required to assess for Klinefelter syndrome (47,XXY). (Choice D) MRI of the brain is indicated if abnormal examination (eg, visual field deficit) or laboratory (eg, hyperprolactinemia) findings are concerning for hypothalamic-pituitary pathology (eg, tumor). This patient has no neurologic deficits, so laboratory testing is indicated before potential imaging. Educational objective: Delayed puberty in boys is defined as lack of testicular enlargement by age 14. The initial evaluation involves obtaining a bone age radiograph and measuring FSH, LH, and testosterone levels. References: Delayed puberty. (http://www.ncbi.nlm.nih.gov/pubmed/22846526)

A 15-Year-Old Boy Is Brought to the Office Due to Concern