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Vulsma et al., Amsterdam and Bilthoven, The Netherlands, determined
the value of additional determination of serum thyroxine-binding globulin
(TBG) for neonatal screening on congenital hypothyroidism (CH). The Dutch
neonatal screening on CH is one of the few examples worldwide, that is
based on measurement of T4 instead of the usual measurement of TSH. TSH
is only being measured in 20% of the lowest T4 concentration. This method
allows congenital CH due to secondary/tertiary causes, but has the disadvan-tage
of false positives due to harmless TBG-deficiency. During a two-years ('93-'94)
nation-wide study TBG was measured in blood spots with 5% lowest T4 concentrations,
and T4/TBG ratios were calculated. During the study period 19 CH patients,
due to secondary/tertiary causes, were detected, and their T4/TBG ratios
were used to define a cut-off point to include them all. By applying this
cut-off point to the whole screening population it is predicted that a
53% reduction in second heelpunctures and a 44% reduction in referrals
to a pediatrician could be effected, and these savings outbalanced the
costs of the additional TBG measurements.
Van Tijn et al., Amsterdam and Leiden, The Netherlands, report further on newborns having TSH-deficiency as detected by "the Dutch method" (low T4 and TSH with normal TBG). They performed MRI studies in 8 subjects with TSH deficiency, 5 having isolated TSH deficiency, and 3 having multiple pituitary deficiences. All these 3 latter patients, and 1 with isolated TSH deficiency, showed posterior pituitary ectopia. The same 3 patients and 2 of the patients with isolated TSH deficiency showed additio-nal cerebral developmental abnormalities, such as corpus callosum dysgenesis and gray matter heterotopia. It is concluded that posterior pituitary ectopia is a frequent and early feature of congenital hypothalamic/pituitary disorders, as found by neonatal screening. Köhler et al., Berlin, Germany, and Amsterdam, The Netherlands, investigated the thyroperoxidase (TPO) gene in 14 children with CH, who had a thyroid gland in the normal position, thus no thyroid dysgenesis. In 3 of 14 patients defects in the TPO gene were found. The authors conclude that future mutation screening of the TPO gene may become an important tool for genetic counselling of patients with early detected and treated CH and a thyroid in the normal position. |
