ESPE Abstracts (2024) 98 RFC12.1

1Bursa Uludag University Faculty of Medicine, Department of Pediatric Endocrinology, Bursa, Turkey. 2Bursa Uludag University Faculty of Medicine, Department of Pediatric Neurology, Bursa, Turkey. 3Bursa Uludag University Faculty of Medicine, Department of Pediatric Cardiology, Bursa, Turkey


The monocarboxylate transporter 8 (MCT8) is essential for transporting thyroid hormones to the brain. MCT8 deficiency occurs in SLC16A2 gene variants; patients usually present with neurological symptoms and are diagnosed with cerebral palsy or central hypothyroidism. Recently, 3,3',5-triiodothyroacetic acid (Triac) is used in treatment. This study aimed to evaluate the diagnosis and follow-up processes of five MCT8 deficiency patients. Five patients with variants in the SLC16A2 gene and clinically compatible with MCT8 deficiency were included in the study. Diagnostic features, genetics, neurological, and cardiac evaluations were presented in Table 1. Neuromotor retardation was present in all cases at the time of diagnosis. A significant difference was found between the age of the first admission and the diagnosis (P = 0.043). Although all cases had an uneventful birth history, all were born with global hypotonicity. In four cases, Triac was initiated. A neurological improvement was noticed by the mothers and us of three patients in the first year of treatment. The most crucial point in this study is delay in diagnosis—all patients presented with neurological complaints such as hypotonia and delay in motor development milestones. Thyroid function tests, especially fT3, should be checked in infants presenting with hypotonia.

Table 1: The characteristics of the patients are summarized.
Developmental Milestones of Gross Motor (year) Holter electrocardiogram
Age at first admission and diagnosis (year) Current Age (year) DNA-protein description, variant classification ft4 (ng/dL),
ft3 (ng/L),
TSH (mU/L)
At diagnosis
Gross motor function classification levels Head Control Sits with support Sits alone Walks Visual evoked potential Brainstem auditory evoked response Somatosensory evoked potential Echocardiography
1 1.2 9 13.5 c.1505A>T,
p.Gln502Leu, Variant of uncertain significance
0.96
2.86
0.93
4 2 3 9 Require physical assistance Prolonged latency P100 potential Normal Prolonged latency P40 and N20 potential Normal
2 0.55 2 4.75 c.1270G>A,
p.Asp424Asn, likely pathogenic
0.75
6.32
0.22
5 No No No No Normal Normal Normal Normal
3 1 1.8 9 c.670T>A,
A224T, pathogenic
0.68
5.58
2.84
2 0.5 0.67 2 3 Normal Normal Normal Normal
4 0.5 2 4 c.740C>T,
p.Pro247Leu, VUS
0.63
6.87
2.11
5 No No No No n/a n/a n/a Normal
5 0.4 1.1 6.67 c.1273G>C,
p.Gly425Arg, VUS
0.78
5.2
1.8
n/a n/a n/a n/a n/a n/a n/a n/a Secundum atrial septal defect

Keywords: MCT-8 deficiency, global hypotonicity, 3,3',5-triiodothyroacetic acid

Volume 98

62nd Annual ESPE (ESPE 2024)

Liverpool, UK
16 Nov 2024 - 18 Nov 2024

European Society for Paediatric Endocrinology 

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