C. Cornette

‘LOW T3 SYNDROME’ IN PATIENTS CHRONICALLY TREATED WITH AN IODINE‐CONTAINING DRUG, AMIODARONE

Cardiac patients treated with the iodinecontaining drug ‘amiodarone’ undergo a significant iodine overload whch can last for months after the drug has been withdrawn. Some patients develop hyperthyroidism and others hypothyroidism. In the hyper‐ or hypothyroid patients, the indices of thyroid function are modified as usually observed in these situations. In the patients remaining euthyroid while taking amiodarone or after its withdrawal, but still under its influence as shown by the iodine overload, a ‘low‐T3 syndrome’ is observed, this state being characterized by a high total T4, a low free T4, a normal T3 resin uptake, a low total T3, a normal free T3, a high r‐T3 and a relative TSH‐unresponsiveness to TRH.

Serum thyroglobulin levels in preterm neonates

Serum thyroglobulin (Tg) levels were determined in preterm neonates. Very high values were found at birth. A significant negative correlation was observed between Tg levels and gestational age. A longitudinal study indicates that a very sharp decrease in Tg levels occurred after birth. Three weeks after birth, the values were close to the values of full‐term neonates. These high hTg values could result either from an increased turnover of hTg or from a lower clearance rate of this iodoprotein.

SCREENING FOR NEONATAL HYPOTHYROIDISM BY THYROXINE AND THYROTROPHIN RADIOIMMUNOASSAYS USING DRIED BLOOD SAMPLES ON FILTER PAPER

A routine and automatized methodology for thyroxine (T4) and thyrotrophin (TSH) radioimmunoassay (RIA) using dried blood samples on filter paper is described. T4‐RIA was performed on one single dot (5 mm diameter equivalent to 4 μl of serum) while two dots were necessary for TSH‐RIA. Reference filter papers were introduced in each assay for quality control. In a preliminary study on 4,155 neonates, samples generally obtained between the 5th–7th day gave a mean ‘dot‐T4′ of 97.95 ± 36.04 nmol/l and a mean ‘dot‐TSH’ of 10.19 mU/l ±8.25, corresponding to 2.47 mU/l of serum. Within an 18‐month period (November 1976‐April 1978), a total of 16.522 neonates have been screened allowing detection of three cases of congenital hypothyroidism (incidence 1: 5507), two cases of congenitally low TBG and thirty‐three cases of transient hypothyroidism.

THE EFFECTS OF MILD IODINE DEFICIENCY ON NEONATAL THYROID FUNCTION

In order to assess neonatal thyroid function in the endemic goitre areas of Greece, T4 and TSH have been measured. Previous studies had shown that in these endemic areas, adults had low T4 but normal TSH values, probably because of an increase in the serum T3 level. In this study, T4 and TSH were measured in dried blood spots from 259 neonates. The fifty‐four full‐term neonates from the Greek endemic villages had a lower T4 value (8·8 ± 0·66 μg/dl SE) but a higher TSH (15·37 ± 1·12 mu/l) than the seventy‐three full‐ term neonates from the non‐endemic villages (T4:10·0 ± 0·33 μg/dl, TSH: 11·93 ± 0·59 mu/l) or the ninety‐eight from Athens (T4:10·0 ± 0·33 μg/dl, TSH: 10·96 ± 0·64 mu/l). Premature neonates, both from Athens and from the endemic areas, have significantly lower T4 and significantly lower TSH values than the full‐term ones from the same areas, probably because of the immaturity of the pituitary‐thyroidal axis. It is concluded from these observations that (a) Neonates suffer more from the consequences of iodine deficiency than adults. The biochemical hypothyroidism reported here may be relevant to the delayed skeletal maturation previously reported from children of these same areas. This emphasizes the need for correcting even moderate iodine deficiency. (b) The occurrence of non‐toxic goitre with normal TSH levels in adults is best explained by assuming that increased TSH stimulation is necessary for goitre formation during neonatal life, but not for goitre maintainance during adulthood. (c) Newborn screening programmes in these areas should take into account the present findings.