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PE30.1-7 | Endocrinology — PBL Case

CLINICAL SETTING

The setting is the paediatric outpatient department of a district hospital in a semi-urban area of Tamil Nadu. Dr Meenakshi, a second-year postgraduate trainee, is conducting a well-baby clinic on a Tuesday morning. She has already seen six neonates when the nursing staff hand her a yellow envelope — a newborn screening report that arrived by post. The neonate, Arjun, is now 12 days old and was born at term after an uneventful delivery. His mother, Kavitha, a 26-year-old first-time mother, brought him in today because 'he sleeps too much and doesn't feed properly.' As Dr Meenakshi opens the envelope, she notes the result: heel-prick TSH 92 mIU/L (cut-off >10 mIU/L = refer). Arjun lies in his mother's arms, eyes barely open, with mild jaundice still visible. His anterior fontanelle feels large, and the nurse notes that he has not passed stool in 3 days.

Trigger 1: The Screening Report and the Drowsy Neonate

Dr Meenakshi examines Arjun. He weighs 3.4 kg (birth weight 3.3 kg — minimal weight gain over 12 days). Temperature 36.1°C. Heart rate 88/min (bradycardia for a neonate). Respiratory rate 34/min. He has mild non-haemolytic jaundice. The anterior fontanelle is 4×4 cm (enlarged) and the posterior fontanelle is palpable. There is a large tongue that protrudes slightly. His cry is hoarse. Abdomen is mildly distended. No umbilical hernia. The newborn screening report shows a heel-prick TSH of 92 mIU/L collected on day 4 of life. Dr Meenakshi recalls that the cut-off is 10 mIU/L. She wonders whether this is a false positive from the neonatal TSH surge or true congenital hypothyroidism.

DISCUSSION POINTS

What is the significance of the neonatal TSH surge? Does a heel-prick TSH of 92 mIU/L on day 4 represent the physiological surge or pathological congenital hypothyroidism?
List all the clinical features in this examination that are consistent with congenital hypothyroidism. What is the pathophysiological explanation for each (e.g., enlarged fontanelle, bradycardia, constipation, hoarse cry, prolonged jaundice)?
What confirmatory investigations must be ordered urgently, and what results would confirm the diagnosis?
If the serum TSH returns as 88 mIU/L with free T4 of 5 pmol/L, what is the diagnosis and what is the urgency of treatment?

Click to reveal Trigger 2: Initiating Treatment and Interpreting the Screening Report (discuss previous trigger first!)

Trigger 2: Initiating Treatment and Interpreting the Screening Report

Serum TSH confirms 88 mIU/L and free T4 is 5 pmol/L (normal 10–25 pmol/L). The diagnosis of primary congenital hypothyroidism is confirmed. Dr Meenakshi prescribes levothyroxine. Kavitha is anxious: 'Doctor, my baby will need medicine forever? Will he be normal? Can I breastfeed while giving this tablet?' A second scenario is then raised by the unit head for small-group discussion: the nursing staff mention that another neonate, Priya (born on the same day as Arjun), had a heel-prick TSH of 12 mIU/L — just above the cut-off. Priya's mother has a known history of Hashimoto's thyroiditis. Priya appears clinically well.

DISCUSSION POINTS

What dose of levothyroxine should Dr Meenakshi prescribe for Arjun? How should the tablet be administered to a neonate? What are the monitoring parameters and targets for the first year of treatment?
How should Dr Meenakshi counsel Kavitha about the long-term prognosis, the importance of adherence, and whether breastfeeding is safe? What would happen if the medicine is stopped?
For Priya with a borderline TSH of 12 mIU/L and a mother with Hashimoto's thyroiditis: how should this screening report be interpreted? What is the risk of transient neonatal hypothyroidism from maternal anti-TPO antibody transfer, and what additional test distinguishes this from permanent congenital hypothyroidism?
Design a systematic approach to interpreting all neonatal thyroid screening reports from a district hospital — who should be recalled, what is the timeline for recall, and at what TSH level should treatment be started without further delay?

Click to reveal Trigger 3: The Emergency Next Door — DKA and Ambiguous Genitalia (discuss previous trigger first!)

Trigger 3: The Emergency Next Door — DKA and Ambiguous Genitalia

Three months later, Dr Meenakshi is now posted in the paediatric emergency department. Two patients arrive in the same hour. The first is Ravi, a 10-year-old boy, brought by his father: 10-day history of polyuria, polydipsia, weight loss of 3 kg. In the ED, his blood glucose is 28 mmol/L (504 mg/dL). Urine dip: glucose 4+, ketones 3+. Blood gas: pH 7.14, HCO3 8 mEq/L. He is drowsy, breathing deeply (Kussmaul respiration), and mildly dehydrated (5%). Serum K+ is 5.6 mEq/L. His weight is 32 kg. The second patient is a 3-day-old neonate referred from a nearby primary health centre — born with ambiguous genitalia. Parents appear distressed. Karyotype sent yesterday returns as 46,XX. 17-OHP is 310 nmol/L. Na 129 mEq/L, K 6.5 mEq/L.

DISCUSSION POINTS

For Ravi: Confirm the diagnosis of DKA and classify its severity. Calculate his fluid deficit and describe the IV fluid management plan for the first 48 hours (total volume, rate, type of fluid). When should potassium be added and at what rate? At what point should insulin infusion be started and at what dose (U/kg/hr)?
What is the most feared complication of DKA management in a child and how is it prevented? What are the clinical warning signs, and how should it be treated if it occurs?
For the neonate with ambiguous genitalia: What is the most likely diagnosis and the two life-threatening features that require immediate treatment? What is the recommended acute treatment (drug name + dose + route)?
How would you counsel the parents of the neonate with ambiguous genitalia about the diagnosis, the process of sex determination, and the timeline for any decisions? What is the role of the multidisciplinary team?

Click to reveal Trigger 4: Precocious Puberty Clinic and the Growth Concern (discuss previous trigger first!)

Trigger 4: Precocious Puberty Clinic and the Growth Concern

Dr Meenakshi is now attending the paediatric endocrine outpatient clinic. She sees two children referred from the school health programme. The first is Ananya, a 7-year-old girl, brought by her mother who noticed breast development 3 months ago. On examination: bilateral breast buds (Tanner stage 2), no pubic hair, no axillary hair. Bone age X-ray: 9 years (2-year advance). Pelvic ultrasound: uterine length 4.5 cm (enlarged for age), ovarian volume 3 mL bilaterally (appropriate). GnRH stimulation test: LH peak 18 IU/L, FSH peak 10 IU/L. The second child is Vikram, an 8-year-old boy, referred by his school nurse because he is 'too short'. Growth chart review shows: height at 3rd centile, crossing down from the 25th centile over 2 years. Growth velocity 3 cm/year. Bone age 6 years. TSH normal. IGF-1 low for age. GH stimulation test peak: 3.8 ng/mL on two separate tests.

DISCUSSION POINTS

For Ananya: Is this precocious puberty by definition? What type (GnRH-dependent or GnRH-independent) does the GnRH stimulation test result indicate, and what is the pathophysiological mechanism? What are the consequences of untreated central precocious puberty on final adult height?
What is the recommended treatment for central precocious puberty (drug class, mechanism, route) and what are the treatment goals? When should treatment be stopped?
For Vikram: What is the likely diagnosis based on the combination of reduced growth velocity, delayed bone age, low IGF-1, and GH stimulation peak <10 ng/mL on two tests? How is this differentiated from constitutional delay of growth and puberty and familial short stature?
What is the recommended treatment for growth hormone deficiency in a child? State the dose, route, frequency, and monitoring plan. What factors predict a good response to treatment?

Group Task Assignments

Group 1: Collaborative Task

Group 2: Collaborative Task

Group 3: Collaborative Task

Learning Issues

Research these questions and bring your findings to the discussion.

[PE30.1] What are the clinical features of congenital hypothyroidism in a neonate, and what is the mechanism behind each feature (bradycardia, enlarged fontanelle, prolonged jaundice, hoarse cry, constipation)?
[PE30.2] How is a newborn thyroid screening report interpreted? What is the physiological neonatal TSH surge, at what age does it resolve, and what confirmatory testing is required for a screen-positive result?
[PE30.3] What are the diagnostic criteria for T1DM vs T2DM in a child, and what is the clinical and laboratory basis for this differentiation in the Indian paediatric context?
[PE30.4] What is the stepwise emergency management of paediatric DKA — from fluid resuscitation to insulin infusion to electrolyte monitoring? What are the specific differences from adult DKA management, and why does paediatric DKA carry a cerebral oedema risk?
[PE30.5] What is the commonest cause of ambiguous genitalia in a 46,XX neonate, what is the mechanism of virilisation, and what constitutes a paediatric endocrine emergency in this context?
[PE30.6] How is precocious puberty defined, classified, and differentiated (GnRH-dependent vs independent) using the GnRH stimulation test? What is the significance of advanced bone age for final adult height?
[PE30.7] What pattern of growth chart data (centile crossing, growth velocity, bone age) constitutes a referral-requiring growth deviation, and what is the diagnostic workup for growth hormone deficiency?