Match the following clinical and laboratory profiles of pediatric patients to the most lik… — USMLE Step 2 CK

Match the following clinical and laboratory profiles of pediatric patients to the most likely underlying endocrine disorder.

Elevated $17$ -hydroxyprogesterone, hyponatremia, hyperkalemia, elevated plasma renin activity, and virilized external genitalia in a $46,\text{XX}$ newborn.Classic $21$ -hydroxylase deficiency
Hypertension, hypokalemia, elevated $11$ -deoxycorticosterone, low cortisol, and female external genitalia in a $46,\text{XY}$ newborn. $17\alpha$ -hydroxylase deficiency
Basal luteinizing hormone (LH) $> 0.3 \text{ mIU/mL}$ , robust LH surge following GnRH stimulation, and advanced bone age in a $6$ -year-old girl with breast development.Central precocious puberty
Low free thyroxine ( $\text{T}_4$ ), markedly elevated thyroid-stimulating hormone (TSH), positive anti-thyroid peroxidase antibodies, and declining growth velocity in a $12$ -year-old girl.Hashimoto thyroiditis

Answer

The correct matches are: Profile 1 (virilized 46,XX with salt wasting) matches Classic 21-hydroxylase deficiency. Profile 2 (46,XY with female genitalia and hypertension) matches 17-alpha-hydroxylase deficiency. Profile 3 (elevated LH and advanced bone age) matches Central precocious puberty. Profile 4 (low free T4 and high TSH) matches Hashimoto thyroiditis.

Each clinical profile uniquely corresponds to the pathophysiology of a specific pediatric endocrine disorder. Classic 21-hydroxylase deficiency leads to salt wasting and androgen excess. 17-alpha-hydroxylase deficiency leads to mineralocorticoid excess and androgen deficiency. Central precocious puberty is characterized by premature HPG axis activation. Hashimoto thyroiditis involves autoimmune destruction of the thyroid gland causing primary hypothyroidism.

Step-by-Step Solution

Analyze the first profile presenting with hyponatremia, hyperkalemia, and virilization in a 46,XX infant.

Matches Classic 21-hydroxylase deficiency.

Lack of aldosterone causes salt wasting, while excess androgens virilize female infants. 17-hydroxyprogesterone is appropriately elevated.

Analyze the second profile presenting with hypertension, hypokalemia, and female genitalia in a 46,XY infant.

Matches 17-alpha-hydroxylase deficiency.

Lack of androgens prevents male genital development, while excess mineralocorticoid precursors (11-deoxycorticosterone) cause hypertension and hypokalemia.

Analyze the third profile presenting with pubertal LH levels (> 0.3 mIU/mL) and breast development in a 6-year-old.

Matches Central precocious puberty.

The robust LH surge to GnRH stimulation confirms gonadotropin-dependent (central) activation of the hypothalamic-pituitary-gonadal axis.

Analyze the fourth profile presenting with low free T4, high TSH, and anti-TPO antibodies.

Matches Hashimoto thyroiditis.

These laboratory findings confirm primary autoimmune hypothyroidism, a common cause of acquired short stature and delayed growth in adolescents.

Key Concept

Identifying characteristic clinical and hormonal patterns in pediatric endocrine disorders, specifically congenital adrenal hyperplasia variants, precocious puberty, and autoimmune thyroiditis.

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