Estudos da função tireóidea em crianças com síndrome de Down.

STUDIES OF T H E THYROID FUNCTION IN

CHILDREN W I T H DOWN'S S Y N D R O M E

BENJAMIN J. SCHMIDT * NELSON CARVALHO * * CLÁUDIO C . ORTEGA*** JOSÉ LIBERMAM * * * JANE M . M . BIAZZI * * * POJUCAN M . TAPAJÓS*** STANISLAU K R Y N S K I * * * *

The study of the thyroid function in Down's syndrome has been the

subject of various contraversal publications, thus clearly showing the existing

doubts within some not too well defined aspects.

Benda's anatomo-pathological works are expressive, showing anatomic

alterations of the thyroid in 47 of the 48 cases studied with Down's syndrome.

Benda et a l i .

.

.

and M y e r s

refer to the importance of the maternal

hypothyroidism in the genesis of mongolism. Various works

,

>

have

shown thyroid functional alterations in mongoloids. On the other hand, some

authors

.

.

have not found alterations of the thyroid function in Down's

syndrome. Saxena et a l .

severely criticize the common and indiscriminated

use of the thyroid hormone in mongoloid patients, once a hypothyroidism

diagnosis has not been previously established. Such doubts and discrepancies

in the specialized bibliography encouraged us in making a study of the

thyroid function in non-institutionalized patients with Down's syndrome, by

comparing the results obtained from normal siblings with almost the same

corresponding ages as the patients studied.

M A T E R I A L S A N D M E T H O D S

T w e n t y nine non-institutionalized children clinically and cytogenetically characte-rized as suffering from Down's syndrome were selected. T h e a g e of the patients ranged from 1 to 1 6 years old, being 18 m a l e s and 1 1 females. T h e T - 3 (tri-iodethyronine) and T - 4 (tetra(tri-iodethyronine) serie levels of all the patients were

dosed and the Im

captation by the thyroid after 2 and 24 hours was measured. T h e results obtained were compared to the others taken from the patient's sibblings, in a total of 39, being 22 m a l e s and 17 females, all clinically normal, aged from 2 to 18 years old.

T h e readings of the radiiodine were m a d e t h r o u g h sparkling detectors supplied with t h a l l i u m activated sodium iodide cristal, m e a s u r i n g 3.5 x 5 cm, in order to reduce to a m i n i m u m the iodine quantity which should be administered to the patient. T h e technique employed followed the norms recommended by the Inter-national A g e n c y of A t o m i c E n e r g y \ T h e tracing doses varied from 2 0 to 3 0 mCi of I "1

. T h e readings were taken in t h e first 2 and 24 hours after the dose w a s administered. T h e fixation percentages of T - 3 on resin were determined, according to the technique recommended by B r o o k e m a n and W i l l i a m s " , w i t h material supplied by the A m e s C o m p a n y . T h e plasmatic T - 4 w a s determined following B r a v e r m a n el al's t e c h n i q u e3

, using the A m e s C o m p a n y patterns.

T h e results obtained f r o m the patients as compared to their n o r m a l siblings shown that there is a significant difference (P < 0 . 0 1 ) in t h e captation of I1 3 1

by t h e thyroid in the first t w o hours. This difference becomes insignificant ( P > 0 . 0 5 ) vihen compared to the results of the 2 4 hour's captation. I n relation to the T - 3 and T - 4 levels, there were no significant differences in the t w o groups studied.

D I S C U S S I O N

In the cases studied, the T-3 and T-4 levels, as well as the captation

of the I

through the thyroid measured 24 hours after the I

that the results obtained from the patients studied were normal. Regarding

the T-3, the works of Kurland et a l .

, Pearse et a l .

, Jackin et a l .

and

Spinelli Ressi and Bergonzi

showed high levels in patients with Down's

syndrome. It must be pointed out that these authors determined the

capta-tion of the T-3 through erythrocyte, a methodology subject to a series of

errors and not up-to-date. Rimoin et al.

, using a similar technique as the

one employed at the present study, did not find significant alterations of

the I

, when comparing the results obtained from mongoloids to the ones

from normal individuals.

Literature data diverge with regard to the captation of the I

through

the thyroid: Pearse et a l .

with 24 hour readings showed a hypocaptant

thyroid in their mongoloids; Cottino et al.

, by taking readings in 1, 24 and

48 hours, found no significant difference after comparing the results to the

normal ones. In the present work the results obtained in the thyroid captation

of the I

when obtained 2 hours after the intake of isotope radium, were

significative (P < 0.01) when compared to the results obtained from the

clinically normal siblings. These results suggest that the mongoloids might

have a deficit of the hypothalamus-hypophyso-thyroid axis, although the levels

of the thyroid captation during the 24 hours reached indexes similar to the

normal; during the first 2 hours the levels were significantly lower than

those found in the controls. The hypothalamus-hypophysary stimulus or the

response of the thyroid gland would be slow but compensated when analyzed

after 24 hours. Such hypothesis unfolds perpectives for new studies within

Down's syndrome.

S U M M A R Y

The thyroid function (T-3 triiodothyronine; T-4 tetraiodothyronine and

the captation of the I

through the thyroid, in 2 and 24 hours after the

intake of isotope radium), was studied in patients with Down's syndrome

and the results being compared to those obtained from the respective siblings,

all clinically normal. The comparative results showed no significant

differen-ces, except in the 2 hours captation of the I

through the thyroid (P < 0.01).

The findings suggest that the hypothalamus-hypophysary or the response of

the thyroid gland would be slow, but compensated when analyzed after

24 hours.

R E S U M O

Estudos da função tireóidea em crianças com síndrome de Down

Os autores estudaram a função tireóidea (T-3, triiodotironina; T-4,

tetraiodotironina e captação do I

normais. Os resultados comparativos não apresentaram diferenças

significa-tivas, exceto na captação de 2 horas do I

pela tireóide (P < 0,01). Os

achados sugerem que o estímulo hipotálamo hipofisário ou a resposta da

glândula tireóide seria lento (a) mas compensado (a) quando analisados após

24 horas.

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Departamento de Pediatria — Escola Paulista de Melicina — Rua Botucatu 720