Identification of Predictors of Transient and Permanent Congenital Hypothyroidism

Constanza Navarro-Moreno; Ana-Lucía Gómez-Gila

Introduction: Congenital hypothyroidism (CH) is classified as permanent CH (PCH) if levothyroxine (LT4) is life-long required, or as transient CH (TCH) if after LT4 discontinuation thyroid function remains normal. Early detection of TCH allows early discontinuation of LT4.

Purposes: To identify predictors of TCH and PCH, and their cut-off value.

Subjects and Methods: Retrospective study of patients aged >3 years diagnosed of CH from 1993. Exclusion criteria: ≤32 weeks of gestation and birth weight ≤1500g. Patients are classified as PCH in case of high TSH after LT4 discontinuation, or compatible thyroid imaging (athyreotic or ectopic gland).

Results:


N=114	PCH (n=92, 80.7%)	N	TCH (n=22, 19.3%)	N	P	-Cut-off value (ROC area) -Cut-off value with specificity >95% for PCH/TCH
Screening TSH (mIU/l)b	101 (23.7-180)	61	15.3 (12.7–18.7)	13	<0.001	≥18.8 (0.83) ≥54.8/<4.61
Diagnosis TSH (mIU/l)b	151 (52.28–425)	87	39 (13.86–59.3)	21	<0.001	≥59.3 (0.85) ≥99.5/<23.6
Diagnosis fT4 (ng/dl)b	0.495 (0.25–1.06)	84	1.14 (0.75–1.61)	20	<0.001	≥ 0.95 (0.76) <0.36/≥1.77
Thyroid imaginga - Apparent aplastic or hypoplastic - Ectopic - In situ - Enlarged	24 (27.59%) 41 (47.13%) 16 (18.39%) 6 (6.9%)	87	2 (12.5%) 11 (68.75%) 3 (18.75%)	16	<0.001
Starting LT4 dose (µg/kg)c	12.91 (3.74)	79	9.81 (3.44)	21	<0.001	≥10.72 (0.74) ≥13.81 / <7.81
6 months LT4 dose (µg/kg/day)b - <3 µg/kg/daya	4.47 (3.75–5.33) 3 (4%)	75	3.11 (2.36 – 3.73) 6 (42.86%)	14	<0.001 <0.001	≥3.74 (0.83) ≥5.12/<3.1
12 months LT4 dose (µg/kg/day)b - <3µg/kg/daya	4.3 (3.7–5.19) 12 (15.19%)	79	2.4 (1.5–2.88) 13 (76.47%)	17	<0.001 <0.001	≥3.15 (0.92) ≥3.87/<2.25
3 years LT4 dose (µg/kg/day)b - <3µg/kg/daya	3.73 (3–4.44) 8 (25.8%)	37	1.7 (1–2.08) 18 (94.7%)	19	<0.001 <0.001	≥2.42 (0.91) ≥2.5/<1.4
^aFrequency ^bMedian (interquartile range) ^cMean (SD) Gestational age, birth weight, TSH and fT4 at age 6 and 12 months do not show significant differences between TCH and PCH groups.

Conclusions: The strongest predictors of PCH are LT4 dose ≥3.15 µg/kg/day at age 12 months, and LT4 dose ≥2.42 µg/kg/day at age 3 years.
While screening TSH <4.61 mIU/l, diagnosis TSH <23.6 mIU/l, diagnosis fT4 ≥1.77 ng/dl, starting LT4 dose <7.81 µg/kg/day, LT4 dose <3.1 µg/kg/day at age 6 months, LT4 dose <2.25 µg/kg/day at age 12 months and LT4 dose <1.4 µg/kg/day at age 3 years individually predict TCH.
These predictors allow to identificate which patients may benefit for an ealy LT4 discontinuation.

ESPE Abstracts

P2-283