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PE30.1-7 | Endocrinology — Practice Quiz
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A 4-day-old neonate is found to have a TSH of 45 mIU/L on heel-prick newborn screening. Repeat confirmatory serum TSH is elevated with low free T4. The baby appears clinically well. Which of the following is the MOST appropriate immediate action?
Congenital hypothyroidism requires early treatment (ideally within 2 weeks of life) to prevent irreversible intellectual disability. Levothyroxine 10–15 mcg/kg/day is started as soon as the diagnosis is confirmed on repeat testing — not deferred to 6 weeks.
Congenital hypothyroidism is the commonest preventable cause of intellectual disability. Heel-prick TSH screening at day 3–5 followed by prompt levothyroxine 10–15 mcg/kg/day is the standard of care.
Delay in starting levothyroxine risks permanent neurodevelopmental harm. Observation alone (A) or deferral pending specialist review (D) are not acceptable. Option B correctly identifies the dose but should follow confirmatory testing rather than precede it.
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A 10-year-old girl is brought with polyuria, polydipsia, and 3 kg weight loss over 3 weeks. Fasting blood glucose is 15 mmol/L (270 mg/dL), urine dip shows glucose 4+ and ketones 2+. She is alert, respiratory rate is 22/min, and there is mild dehydration. Which of the following best describes her condition and the initial priority?
This child has new-onset T1DM presenting with mild DKA (ketones + acidosis indicators). Mild-to-moderate DKA is managed with IV fluid rehydration (spread over 48 hours to reduce cerebral oedema risk) and insulin infusion at 0.05–0.1 U/kg/hr after the first hour of fluids.
Paediatric DKA management: IV rehydration over 48 hours (to reduce cerebral oedema risk), then insulin infusion at 0.05–0.1 U/kg/hr; monitor for cerebral oedema — the commonest fatal complication.
T2DM is uncommon in a lean child with acute-onset symptoms and ketonuria — metformin (A) is wrong. Stress hyperglycaemia (C) does not produce this degree of glycosuria/ketonuria with weight loss. Option D misses the DKA, which requires IV fluids before insulin.
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A 14-year-old boy with known T1DM is brought to the emergency department unresponsive. His blood glucose is 32 mmol/L (580 mg/dL), blood gas shows pH 7.12, bicarbonate 8 mEq/L, and urine ketones are strongly positive. He is severely dehydrated. Which rate of insulin infusion is appropriate once fluids have been running for 1 hour?
Current ISPAD guidelines recommend starting insulin infusion at 0.05–0.1 U/kg/hr after the first hour of IV fluid resuscitation in paediatric DKA. Insulin boluses are no longer recommended as they increase cerebral oedema risk.
In paediatric DKA: no insulin bolus; start insulin infusion at 0.05–0.1 U/kg/hr after 1 hour of IV rehydration. Watch for cerebral oedema — headache, slowed heart rate, and deteriorating consciousness are warning signs.
0.01 U/kg/hr (A) is sub-therapeutic. 0.3 U/kg/hr (C) is too rapid and risks hypoglycaemia and electrolyte shifts. Insulin boluses (D) are contraindicated in paediatric DKA per current guidelines.
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A neonate is born with ambiguous genitalia. On examination, there are labioscrotal folds, a phallus 2 cm in length, and no palpable gonads bilaterally. Electrolytes show Na 128, K 6.2 mEq/L. What is the MOST likely underlying cause and the critical emergency to address?
CAH due to 21-hydroxylase deficiency is the commonest cause of ambiguous genitalia in a 46,XX neonate. Salt-wasting form presents with hyponatraemia and hyperkalaemia — a life-threatening adrenal crisis requiring emergency IV hydrocortisone (25 mg/m² stat) and isotonic saline. Sex assignment must never be hasty — it requires karyotype + 17-OHP + MDT discussion.
CAH (21-hydroxylase deficiency) is the commonest cause of ambiguous genitalia in a 46,XX infant. Salt-wasting crisis is a paediatric emergency — treat with IV hydrocortisone and saline immediately. Karyotype + 17-OHP before any sex assignment.
CAIS (A) presents with 46,XY with no palpable gonads but has normal female external genitalia (not ambiguous phallus). Turner (C) is 45,X female with no ambiguous genitalia. True hermaphroditism (D) is rare, and sex assignment by appearance alone is unacceptable.
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An 8-year-old girl is referred for breast development noticed by her parents. On examination, bilateral breast bud development (Tanner stage 2) is present. Pubic hair is absent. Her bone age is 2 years advanced. LH/FSH are elevated after GnRH stimulation. Which of the following is the MOST likely diagnosis?
Precocious puberty in girls is defined as secondary sexual characteristics before age 8 years. Elevated LH/FSH after GnRH stimulation with advanced bone age indicates gonadotropin (GnRH)-dependent (central) precocious puberty, driven by premature activation of the HPG axis.
Precocious puberty: onset of secondary sexual characteristics before age 8 years (girls) or 9 years (boys). Elevated LH/FSH after GnRH stimulation = central (GnRH-dependent). Advanced bone age risks reduced final height — refer for GnRH analogue therapy.
Premature thelarche (A) shows isolated breast development with normal bone age, normal LH/FSH. GnRH-independent (peripheral) precocious puberty (B) has suppressed LH/FSH (not elevated) because the source is autonomous (ovarian/adrenal). At 8 years with advanced bone age, this is not normal (D).
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During a well-child visit, a 9-year-old boy's height is plotted at the 3rd centile, down from the 25th centile on charts from 18 months ago. His weight is at the 10th centile. He has no dysmorphic features, eats well, and has a normal physical examination. Which of the following is the MOST appropriate next step?
Crossing 2 or more major centile lines downward over 18 months represents abnormal growth velocity and is a red flag indicating pathological growth failure. This warrants early referral for evaluation (thyroid function, bone age, growth hormone assessment, coeliac screen, etc.).
Abnormal growth velocity (crossing centile lines downward) is a key red flag. Screen for hypothyroidism, GH deficiency, coeliac disease, chronic illness, and psychosocial causes. Bone age X-ray is an early, low-cost investigation.
Familial short stature (A) does not cause centile crossing — the child stays parallel to their familial centile. Watching for 6 more months (C) delays potentially treatable causes. Dietary supplements (D) without diagnosis can miss GH deficiency, hypothyroidism, or coeliac disease.
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A 7-day-old neonate born at term has a screening TSH of 60 mIU/L. The mother's thyroid function is normal. The baby has prolonged jaundice, large anterior fontanelle, and lethargy. Serum confirms primary congenital hypothyroidism. What is the MOST appropriate initial levothyroxine dose?
The standard starting dose for congenital hypothyroidism is levothyroxine 10–15 mcg/kg/day, given orally in a crushed tablet mixed with breast milk (not soy formula). The goal is to normalise TSH within 2–4 weeks and achieve a free T4 in the upper half of the reference range promptly.
Congenital hypothyroidism: 10–15 mcg/kg/day levothyroxine orally, starting within 2 weeks of birth. Prolonged jaundice, large fontanelle, lethargy, and constipation are classical clinical clues to the diagnosis.
5 mcg/kg/day (A) is sub-therapeutic and delays normalisation of thyroid status, prolonging neurodevelopmental risk. Fixed adult doses (C) are never appropriate in neonates — all paediatric dosing is weight-based. 2–5 mcg/kg/day (D) is too cautious; rapid normalisation is the clinical goal.
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A urine dipstick on a 12-year-old girl with polyuria and polydipsia shows glucose 3+ and ketones 3+. Her blood glucose is 22 mmol/L (396 mg/dL). She is drowsy but responds to voice. Blood gas: pH 7.18, HCO3 10 mEq/L. Which of the following is the MOST important immediate concern in her management?
Cerebral oedema is the leading cause of death in paediatric DKA, occurring in 0.5–1% of episodes, typically within 4–12 hours of starting treatment. It is linked to overly rapid or hypotonic fluid administration and is the rationale for spreading rehydration over 48 hours. Any deterioration in consciousness during DKA treatment should prompt immediate mannitol or hypertonic saline.
Cerebral oedema is the main DKA-related cause of death in children. Prevent it by spreading IV fluids over 48 hours, using isotonic saline, and avoiding excess free water. Monitor consciousness hourly; give mannitol 0.5–1 g/kg IV stat if cerebral oedema is suspected.
Hypoglycaemia (A) is a valid concern later in treatment but is not the leading cause of death. Hyperkalaemia (C) is present before insulin but the concern reverses to hypokalaemia once insulin starts and K+ shifts intracellularly. Aspiration (D) is a risk but is not the primary DKA-specific danger.
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A 6-year-old boy is referred by his school for poor academic performance and short stature. Growth chart review shows height at −2.5 SD with a bone age of 4 years. Thyroid function is normal. IGF-1 is low for age. GH stimulation test shows a peak GH of 4 ng/mL (normal >10 ng/mL). What is the diagnosis?
Peak GH <10 ng/mL on stimulation testing + low IGF-1 + delayed bone age in a child with growth failure = growth hormone deficiency (GHD). Treatment is recombinant GH at 25–50 mcg/kg/day SC. Referral to a paediatric endocrinologist for GH therapy is mandatory.
Diagnose GH deficiency: two GH stimulation tests with peak GH <10 ng/mL, supported by low IGF-1 and delayed bone age. Treatment: recombinant GH 25–50 mcg/kg/day SC, best response when started early before bone plates fuse.
Familial short stature (A) has normal bone age and normal growth velocity. CDGP (B) also has delayed bone age but with a positive family history and normal GH/IGF-1. Psychosocial short stature (D) requires an adverse psychosocial environment and should improve with removal from that environment.
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A 13-year-old girl has had no breast development and no menarche. She is 145 cm (well below the 3rd centile). Karyotype returns as 45,X. On examination there is a low hairline and webbing of the neck. Which of the following is the MOST appropriate management plan?
Turner syndrome (45,X) causes primary ovarian failure and growth failure. Management involves: (1) recombinant growth hormone to maximise final height (started early, before 12 years ideally); (2) low-dose oestrogen at approximately 12–13 years to induce puberty, progressively increased over 2–3 years, then cyclic oestrogen-progesterone for endometrial protection.
Turner syndrome (45,X): short stature + delayed puberty + streak gonads. Treatment: GH therapy for height, oestrogen induction at 12–13 years. Screen for cardiovascular (aortic coarctation, bicuspid valve), renal, and thyroid complications.
Waiting until age 16 (B) unnecessarily delays pubertal induction and risks poor bone density and psychosocial consequences. Reassurance alone (C) is inappropriate — Turner syndrome requires active multi-system management. GnRH analogues (D) suppress puberty (used in precocious puberty) — the opposite of what is needed here.
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