Autonomy in endemic goiter.

The occurrence of hyperthyroidism in many individuals after introduction of iodine prophylaxis in endemic goiter areas can have dramatic consequences for the affected individuals. It indicates that in such individuals the increase of serum thyroid hormone level in response to iodine supplementation does not exert its normal negative feedback on thyroid activity, ie, that in such individuals some thyroid tissue has become autonomous. In this short review we summarize what is known about the possible mechanisms, cause, diagnosis, and consequences of thyroid autonomy.

The effects of different doses of oral iodized oil on goiter size, urinary iodine, and thyroid-related hormones.

The prevention of iodine deficiency is still a worldwide concern. This study, conducted in Soja in western Sudan, was carried out to evaluate the effects of a dose of iodized oil sufficient enough to give maximum protection against goiter and provide an acceptable iodine supply without side-effects over a sufficiently long period of time. Adult goitrous subjects (n = 117) were randomly assigned to three groups, A, B, and C, and received a single oral dose of 200, 400, or 800 mg iodine, respectively. Urine and blood samples were collected at the start of the study and monitored for 1 yr. In the 3 groups, mean serum T4 and median urinary iodine and serum TSH values were restored to reference limits, and these were maintained for about 1 yr. In each treatment group, about two thirds of the subjects displayed a reduction in goiter size, and the 400- and 800-mg doses were not more efficient than the 200-mg dose to accomplish normalization of thyroid hormone values. A temporary rise in TSH was noted 1 week after iodine administration in 1, 3, and 10 subjects, respectively, and 1, 0, and 3 subjects showed biochemical signs of thyrotoxicosis during the year after treatment with the 3 different doses. The data indicate that oral administration of 200 mg iodine is effective and acceptable for treating iodine deficiency in adults for 1 yr. Because of the risks of side-effects and the shortage of medical resources, higher doses are not recommended.

Efficacy of low oral doses of iodized oil in the control of iodine deficiency in Zaire.

BACKGROUND: About one billion people worldwide are at risk for iodine deficiency. Despite existing programs of prophylaxis, the prevention of iodine deficiency is still a challenge throughout the developing world. We studied the efficacy of low doses of iodized oil in an area of severe iodine deficiency in Zaire. METHODS: Seventy-five subjects with visible goiter were randomly assigned to receive a single oral dose of placebo or either 0.1 or 0.25 ml of iodized oil, corresponding to 0, 47, and 118 mg of iodine, respectively. The mean ages of the subjects in the three groups were 23, 22, and 22 years, respectively, and the ratios of males to females were 0.25, 0.32, and 0.19. Efficacy was assessed by evaluating goiter size and measuring urinary iodine and serum thyroid hormone concentrations for 12 months. RESULTS: Goiter size decreased in most of the subjects who received either dose of iodized oil. Their urinary iodine concentrations were normal for six to nine months and their serum thyroxine and thyrotropin concentrations were nearly all normal throughout the study period. There were no side effects, even in subjects whose serum thyroxine concentrations had initially been low. In the placebo group, neither goiter size nor any of the biochemical values changed. CONCLUSIONS: The oral administration of a single small dose of iodized oil is capable of correcting iodine deficiency for about a year. This method of supplementation is likely to be more effective, efficient, and acceptable than the administration of either intramuscular or large oral doses of iodized oil.

Reversibility of severe hypothyroidism with supplementary iodine in patients with endemic cretinism.

The reversibility of thyroid dysfunction in children with endemic cretinism treated with supplemental iodine is unknown. To study this question we conducted a five-month follow-up of 51 patients with cretinism (age 14 and below), who were randomly assigned to treatment (0.5 ml of intramuscular iodized oil) and control groups. The geometric mean initial serum level of thyrotropin (223 microU per milliliter; SD, 97 to 513) and the mean (+/- SD) initial serum level of thyroxine (1.0 +/- 1.2 micrograms per deciliter) indicated that all patients had severe hypothyroidism. Within one month after receiving the iodized oil, 13 of 14 of the younger patients (less than 4 years) and 1 of 9 of the older patients (4 to 14 years; P less than 0.001) had thyrotropin values below 20 microU per milliliter. Five months after treatment, the levels of thyrotropin had decreased and those of thyroxine had increased in all children, but greater changes occurred in the 13 younger patients than in the 14 older patients. The mean levels of thyrotropin were 2 microU per milliliter (SD, 0.6 to 6) vs. 38 microU per milliliter (SD, 11 to 132; P less than 0.001), and the mean (+/- SD) levels of thyroxine were 13.1 +/- 2.8 vs. 8.1 +/- 4.6 micrograms per deciliter (P less than 0.001). In the untreated group, 3 of the 9 younger patients and none of the 15 older patients recovered normal thyroid function within five months. We conclude that iodine supplementation restored a biochemically euthyroid state in all younger children with cretinism but only some of the older children. In addition, some younger patients became euthyroid without iodine supplementation.

Endemic infantile hypothyroidism in a severe endemic goitre area of central Africa.

Thyroid function and exposure to dietary goitrogenic factors (iodine deficiency and thiocyanate overload) were studied at birth and from birth to 7 years in 200 neonates and 347 children living in the severe endemic goitre area of Ubangi, Northern Zaire. Serum T4 was at the lower limit of normal at birth (104 +/- 4 nmol/l) and stayed at that level during the first year of life (123 +/- 9) (NS), but decreased to 75 +/- 8 (P less than 0.001) at 2-4 years and to 62 +/- 6 (P less than 0.001) at 5-7 years of age. Mean serum FT4 decreased from 10.4 +/- 0.9 pmol/l during the first year to 8.2 +/- 1.0 (NS) at 2-4 years (NS) and to 7.7 +/- 0.9 (P less than 0.05) at 5-7 years. Mean serum TSH was 10.4 (8.4-12.9) mU/l (geometric mean +/- 1 SEM) during the first year, 10.1 (7.5-13.7) (NS) at 2-4 years and 24.3 (18.5-31.9) (P less than 0.05) at 5-7 years. Mean serum T3 was 3.23 +/- 0.12 nmol/l during the first year and remained stable thereafter. The frequencies of low T4 (T4 less than 77 nmol/l), high TSH TSH (TSH greater than 50 mU/l), and low T4 and T3 (T3 less than 1.69 nmol/l) were twice as high at 5-7 years as in the first year (respectively 65%, 42% and 15%). The urinary iodide concentration of the children was stable and low throughout the study period. By contrast, serum thiocyanate concentration which was high at birth (129 +/- 5 mumol/l) decreased to normal values between 3 and 12 months of age and increased again during and after weaning (1 to 3 years of age) to reach a value of 138 mumol/l which was comparable to that observed in adults in the same area. Thiocyanate concentration was high (133 +/- 7 mumol/l) in the mothers' serum but low in the mothers' milk (57 +/- 3 mumol/l) (P less than 0.001). Multivariate analysis showed that both iodine deficiency and thiocyanate overload were explanatory factors of the serum levels of T4, FT4 and TSH in children. In conclusion, our results show that infantile hypothyroidism is much more frequent at 5-7 years of age than at birth or during the first year of life. The deterioration in thyroid function during and after weaning is linked to persistent iodine deficiency accompanied by an increase in thiocyanate overload. The variability in the age of onset, the severity, and the duration of infantile hypothyroidism might explain the wide range of psychomotor and physical abnormalities observed in a large proportion of subjects in this area.

PIP: Thyroid function and exposure to dietary goitrogenic factors (iodine deficiency and thiocyanate overload) were studied at birth and from birth to 7 years in 200 neonates and 347 children living in the severe endemic goiter area of Ubangi, Northern Zaire. Serum T4 was at the lower limit of normal at birth (104 +or- 4 nmol/1) and stayed at that level during the 1st year of life (123 +or- 9) (NS), but decreased to 75 +or- 8 (P0.001) at 2-4 years and to 62 +or- 6 (P.001) at 5-7 years of age. Mean serum FT4 decreased from 10.4 +or- 0.9 pmol/1 during the 1st year to 8.2 +or- 1.0 (NS) at 2-4 years (NS) and to 7.7 +or- 0.9 (P0.05) at 5-7 years. Mean serum TSH was 10.4 (8.4-12.9) mU/1 (geometric mean +or- 1 SEM) during the 1st year, 10.1 (7.5-13.7) (NS) at 2-4 years, and 24.3 (18.5-31.9) (P0.05) at 5-7 years. Mean serum T3 was 3.23 +or- 0.12 nmol/1 during the 1st year and remained stable thereafter. The frequencies of low T4 (T477 nmol/1), high TSH TSH (TSH50 mU/1), and low T4 and T3 (T31.69 nmol/1) were twice as high at 5-7 years as in the 1st year 65%, 42%, and 15%, respectively). The urinary iodide concentration of the children was stable and low throughout the study period. By contrast, serum thiocyanate concentration which was high at birth (129 +or- 5 cmol/1) decreased to normal values between 3-12 months of age and increased again during and after weaning (1-3 years of age) to reach a value of 138 umol/1 which was comparable to that observed in adults in the same area. Thiocyanate concentration was high (133 +or- 7 umol/1) in the mothers' serum but low in the mothers' milk (57 +or- 3 umol/1) (P0.001). Multivariate analysis showed that both iodine deficiency and thiocyanate overload were explanatory factors of the serum levels of T4, FT4, and TSH in children. The results show that infantile hypothyroidism is more frequent at 5-7 years of age than at birth or during the 1st year of life. The deterioration in thyroid function during and after weaning is linked to persistent iodine deficiency accompanied by an increase in thiocyanate overload. Variability in age at onset, severity, and duration of infantile hypothyroidism might explain the wide range of psychomotor and physical abnormalities observed in a lage proportion of subject, in this area.

Strategy of goitre and cretinism control in Central Africa.

Goitre prevalence in Ubangi Mongala (north-western Zaïre) ranges from 27 to 60 per cent in the male population and from 48 to 78 per cent in the female population; the prevalence of cretinism ranges between 0.7 and 7.6 per cent. This severe endemia affects 1.5 million inhabitants and constitutes a major public health problem. If administered to an entire population, single injections of slowly resorbable iodized oil can reduce goitre prevalence substantially, correct the iodine deficiency and restore normal thyroid function for a period of 3 to 7 years, depending on the parameter considered. The cost of programme of endemic goitre prevention based on this method can be estimated at 0.07 US dollars per person and per year of protection. A strategy of goitre and cretinism control in Central Africa, using iodized oil in an attack phase and iodized salt in a follow-up phase, is proposed. The organization of this programme will be dovetailed into other public health activities and will strengthen the basic health service framework.

PIP: Goiter prevalence in Ubangi Mongala (northwest Zaire) ranges from 27-60% in the male population and from 48-78% in the female population; the prevalence of cretinism ranges from 0.7-7.6%. The severe endemia affects 1.5 million inhabitants and constitutes a major public health problem. If administered to an entire population, single injections of slowly resorbable iodized oil can reduce goiter prevalence substantially, correct the iodine deficiency, and restore normal thyroid function for a period of 3-7 years, depending on the parameter considered. The cost of such a program of endemic goiter prevention based on this method can be estimated at 0.07 US dollars/person/year of protection. A strategy of goiter and cretinism control in Central Africa, using iodized oil in an attack phase and iodized salt in a follow-up phase is proposed. The organization of this program will be dovetailed into other public health activities and will strengthen the basic health service framework.