A 3-year-old girl is brought to the physician by her parents for complaints of breast development and pubic hair growth for the past 6 months. She has no significant birth or medical history. The temperature is 37.0°C (98.6°F), the pulse is 88/min, and the respirations are 20/min. Physical examination shows enlarged breasts at Tanner stage 3 and pubic hair at stage 2. Height and weight are in the normal range. On GnRH stimulation testing, a luteinizing hormone (LH) response of < 5 IU/L is detected. What is the most appropriate next step in diagnosis?

Measure baseline estradiol levels and perform pelvic ultrasound

Perform leuprolide stimulation test to measure testosterone

Measure FSH levels to evaluate pituitary function

Calculate LH:FSH ratio from previous GnRH test

Repeat GnRH stimulation test to confirm LH response

An otherwise healthy 13-year-old boy is brought to the physician for the evaluation of severe acne for the last 3 years. Topical retinoic acid and oral tetracycline did not improve his symptoms. He shaves his chin and mustache area every few days. His parents report that he grew 5 cm (2 in) during the last year. The onset of pubic hair growth was at age 8. He is at the 95th percentile for height and weight. Vital signs are within normal limits. Examination shows several pimples and pustules along the skin of the cheeks, chin, and neck. Genitals are Tanner stage 4 and pubic hair is Tanner stage 5. Early morning serum laboratory studies drawn 30 minutes after administration of ACTH show: Sodium 137 mEq/L Potassium 3.8 mEq/L Cortisol (0800 h) 4 μg/dL Aldosterone 10 ng/dL (N = 7–30) 17OH-Progesterone 230 ng/dL (N = 3–90) Deoxycorticosterone 2.7 ng/dL (N = 3.5–11.5) Androstenedione 350 ng/dL (N = 80–240) Dehydroepiandrosterone sulfate (DHEAS) 420 μg/dL (N = 29–412) Which of the following is the most likely underlying cause of this patient's symptoms?

Constitutive activation of adenylyl cyclase

Leydig-cell tumor production of androgens

A 3-year-old girl is brought to the physician by her mother two days after the sudden onset of a rash. The mother says that the rash developed an hour after she bathed the child in hot water. Two weeks ago, the patient was diagnosed with a skin infection and was treated with penicillin V. She has been otherwise healthy but has missed several well-child examinations. She lives with her single mother, who recently lost her job and is now dependent on social assistance. The patient's mother has major depressive disorder and her maternal aunt has systemic lupus erythematosus. The girl's temperature is 36.8°C (98.2°F), pulse is 112/min, and blood pressure is 108/62 mm Hg. She has poor eye contact. Physical examination shows sharply delineated erythema on the lower extremities up to the umbilicus with sparing of the knees and flexor surfaces. Further evaluation is most likely to reveal which of the following?

Multiple injuries in different stages of healing

Malar rash with sparing of the nasolabial folds

Puberty stages (Tanner stages) for USMLE Step 1: High-Yield Pediatrics Lessons

Tanner Stages - Puberty's Roadmap

A 5-stage scale for tracking physical development. Pubic hair progresses from sparse/straight (Stage II) to coarse/curly, covering the mons and spreading to thighs (Stage V).

⭐ Thelarche (breast budding) is the first sign in girls (Stage II). Testicular enlargement (>4ml or >2.5 cm) is the first sign in boys (Stage II).

Stage	Female: Breast Development	Male: Genital Development
I	Pre-adolescent	Pre-adolescent
II	Breast bud forms	Testes enlarge (>4ml)
III	Breast & areola enlarge	Penis lengthens
IV	Areola/papilla form secondary mound	Penis widens, glans develops
V	Mature, single contour	Mature size & shape

Female Tanner Stages - Thelarche & Pubarche

Sequence: Thelarche (Breast) → Pubarche (Hair) → Growth Spurt → Menarche
Thelarche (Breast) typically begins around age 10-11.
Pubarche (Pubic Hair) typically begins ~6-12 months after thelarche.

Female Tanner Stages: Breast and Pubic Hair Development

Stage	Breast Development (Thelarche)	Pubic Hair (Pubarche)
1	Pre-adolescent; papilla elevated only	No true pubic hair
2	Breast bud stage; small mound, ↑ areola diameter	Sparse, long, lightly pigmented hair on labia majora
	> ⭐ Thelarche is the first sign of puberty in ~85% of girls.
3	Breast & areola enlarge; no contour separation	Darker, coarser, curlier hair spreading over mons pubis
4	Secondary mound: areola & papilla project above breast	Adult-type hair, but area covered is smaller
5	Mature: papilla projects, areola recessed to breast contour	Adult-type hair in quantity and distribution; spread to medial thighs

Male Tanner Stages - Gonadarche & Pubarche

Tanner I (Prepubertal):
- Testicular volume < 1.5 ml.
- No pubic hair.
Tanner II (Pubarche):
- Testicular volume 1.6-6 ml.
- Scrotum thins & reddens.
- Sparse, long, downy hair, mainly at the base of the penis.
⭐ Testicular enlargement (gonadarche) is the first sign of puberty in boys, typically occurring around age 11.5.
Tanner III:
- Testicular volume 6-12 ml.
- Penis lengthens.
- Darker, coarser, curlier hair spreads over the pubic symphysis.
Tanner IV:
- Testicular volume 12-20 ml.
- Penis grows in length and circumference; glans develops.
- Coarse, adult-like hair, but not on thighs.
Tanner V (Adult):
- Testicular volume > 20 ml.
- Adult genitalia size and shape.
- Hair extends to the medial thighs.

Tanner Stages of Male Genital and Pubic Hair Development

Puberty Timing - Clocking In & Out

Normal Onset (Girls): 8-13 years.
- 📌 Mnemonic: B-A-M → Breast (Thelarche) → Axillary/Pubic Hair (Adrenarche) → Menarche.
Normal Onset (Boys): 9-14 years.
- First sign: Testicular enlargement.
Precocious Puberty: Onset of secondary sexual characteristics before:
- Girls: < 8 years.
- Boys: < 9 years.
Delayed Puberty: Absence of pubertal signs by:
- Girls: > 13 years (no thelarche).
- Boys: > 14 years (no testicular enlargement).

Puberty timeline: normal development in girls and boys

⭐ The first sign of puberty in boys is testicular enlargement (volume ≥ 4 ml or length ≥ 2.5 cm), NOT the appearance of pubic hair (pubarche).

High‑Yield Points - ⚡ Biggest Takeaways

Thelarche (breast budding) is the first sign of puberty in girls.

Gonadarche (testicular enlargement >4ml or 2.5cm) is the first sign in boys.

Pubarche (pubic hair) is due to adrenal androgens (adrenarche).

Menarche typically occurs at SMR 3-4, about 2-2.5 years after thelarche.

Precocious puberty is onset before 8 years in girls and 9 years in boys.

Delayed puberty is no signs by 13 years in girls or 14 in boys.

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