Epidemiology of palpable goiter in Greater Buenos Aires, an iodine-sufficient area
Hugo Niepomniszcze, Monica Sala, Karina Danilowicz, Fabian Pitoia, Oscar Bruno
División Endocrinología, Hospital de Clínicas José de San Martín, Facultad de Medicina, Universidad de Buenos Aires
Postal address: Dr. Hugo Niepomniszcze, Av. Forest 335, 1427 Buenos Aires, Argentina. Fax: (54-11) 4555-0472 e-mail: hniepom@elsitio.net
Abstract
The Hospital de
Clínicas organized
a free program of goiter detection by palpation. This campaign was
aimed at the population of the metropolitan area of Greater Buenos Aires (11
million inhabitants), with the prerequisite that each participant should be
quite unaware whether he/she was a carrier of any thyroid disease. Attendees
were split into two groups, i.e., Random and Induced. The former consisted of
542 individuals who came to consultation due to mere curiosity, while the
latter involved 500 subjects, comprising consanguineous family members of
patients with thyroid disorders and also individuals who suffered from other
ailments. Ages ranged from 2 to 85 years. In the Random Group, goiter
prevalence of 8.7% was observed, while in the Induced Group it climbed to
14.4%. Since both groups were mostly made up of women (87.2%), a correction
based on the masculinity index was applied to members of the Random Group. Thus,
the total observed prevalence of goiter was 6%, diffuse goiters corresponding
to 3.5% and nodular ones to 2.5%. The frequency of nodules increased with age,
90.5% occurring in those over 40 years. In the Induced Group, goiter prevalence
among relatives of patients with thyroid disorders proved to be 13.1%, rising
to 17.8% in those who suffered from other complaints. The epidemic data
presented herein are the first arising from a screening survey carried out in
a large iodine-sufficient population of the southernmost tip of the American
continent. These results are useful to build up the world map of goiter
prevalence in non-endemic areas.
Key words: Epidemiology; Goiter; Thyroid; Iodine; Buenos Aires, Argentina
Resumen
Epidemiología del bocio palpable en el
Gran Buenos Aires, un área suficiente en yodo. El Hospital de Clínicas organizó un
programa gratuito para la detección de bocio por palpación. Esta campaña estuvo
dirigida a la población del área metropolitana del Gran Buenos Aires, con el
prerrequisito de que cada participante debía desconocer si padecía alguna
enfermedad tiroidea. De acuerdo a las motivaciones que llevaron a los pacientes
a la evaluación, se dividieron en 2 grupos: Randomizado e Inducido. El primero
consistió de 542 individuos que consultaron por mera curiosidad, mientras que
el segundo involucró a 500 sujetos que tenían familiares con enfermedades
tiroideas e individuos que sufrían otras enfermedades. Las edades oscilaron
entre 2 y 85 años. En el Grupo Randomizado, la prevalencia de bocio fue del
8.7%, mientras que en el Grupo Inducido ascendió a 14.4%. Debido a que ambos
grupos estaban compuestos en su mayoría por mujeres (87.2%), se realizó una
corrección al Grupo Randomizado, basada en el índice de masculinidad. Luego de
esta corrección, la prevalencia total de bocio fue del 6%: difusos 3.5% y
nodulares 2.5%. La frecuencia de nódulos tiroideos se incrementó con la edad,
el 90.5% de los sujetos con nódulos tenía más de 40 años. En el Grupo Inducido,
la prevalencia de bocio entre familiares de pacientes con tiroideopatías fue
del 13.1%, ascendiendo a 17.8% en aquellos que presentaban otros síntomas.
Estos datos son los primeros presentados luego de un screening en una
gran área suficiente en yodo de la región más austral del continente Americano
y son útiles para construir el mapa mundial de prevalencia de bocio en áreas no
endémicas.
Palabras clave: Epidemiología; Bocio; Tiroides; Yodo; Buenos Aires; Argentina
Among the activities of the Hospital
de Clínicas José de San
Martin, belonging to the School of Medicine, University of Buenos Aires,
campaigns for the detection of diverse diseases are contemplated. This program
is based on devoting one complete week to study the general population free of
charge, mainly of Buenos Aires City and the 24 Districts of Greater Buenos
Aires, interested in the pathology chosen for the respective time slot. Thus,
the corresponding Service organizes, within its logistical and economic
resources, the type and scope of the mentioned weekly programs. Accordingly,
the Endocrinology Division organized the Thyroid Survey Week (Detection of
Goiter) from Monday 3 to Friday 7 of December 2001. This survey was exclusively
intended for goiter detection in individuals who had no prior knowledge that
they suffered from a thyroid disorder, but were interested in knowing their
condition. For such a reason, patients who knew in advance that they were
carriers of some thyroid pathology, and were therefore under evaluation and/or
treatment, were not included in the study.
The summons to the population was carried out through
informative brochures, posters displayed in the Hospital facilities, and mainly
by mass press media (newspapers, radio and television). In the invitation to
attend, stress was laid on apparently healthy family members of patients with
thyroid disorders and also on carriers of other ailments liable to be
associated to thyroid problems (e.g., vitiligo and rheumatoid arthritis, among
others). At any rate, emphasis was also laid on the convenience that any
citizen, without gender or age restrictions, was free to come to consultation
due to mere curiosity, though lacking any predisposing family and/or personal
history.
Patients and Methods
Campaign design
Individuals interested in participating in this campaign were initially subjected to an orientation consultation to check that those to be studied met the prerequisite of not knowing whether they suffered from any thyroid disease. In cases where the interested parties were aware of their thyroid pathology, they were invited to be seen at our Endocrinology Division, but automatically excluded from this survey of goiter detection. The individual who was admitted to the program, was palpated by one of the authors of this paper, and at the same time asked whether he/she had consanguineous family members (parents, children, siblings, grandparents and uncles/aunts) with any thyroid disease and what was the reason for having decided to participate in the study. Besides, it was proven that the participants were almost entirely permanent residents of the metropolitan area of Buenos Aires City and Greater Buenos Aires. Individuals palpated for goiter were at once referred to the medical endo-crinology resident whose workplace was only a few meters from the physician in charge of palpation. This professional explained to the patient the meaning of the finding, recorded personal data, and requested the pertinent thyroid studies. The physician in charge of palpation classified the goiter type by means of a written code (see Table 1) that was given to the patient so that, in turn, it was handed over to the medical resident.
TABLE
1.- Palpation
Codes
As part of the medical team, a total of 21 examiners (11 physicians and 10 medical undergraduates) participated in this survey. There were two teams in charge of palpation, working simultaneously. Each one of them had a physician in charge, seconded by a medical undergraduate who collaborated with the conducted questionnaire and filling the corresponding form. Patients were derived to the physician in charge of palpation, alternatively, by the students in charge of the orientation consultation. Thus, either team examined 50% of the individuals that attended the campaign. Physicians in charge of palpation were the following authors: HN, MS, KD and FP.
Patients
Drawn by the Thyroid Survey Week, around 1500 individuals, out of whom 1042 met the requirement of being unaware of their previous thyroid status, gathered in the Hospital. Among admitted and palpated individuals, whose ages ranged from 2 to 85 years, 909 (87.2%) were women and 133 (12.7%) men. According to the conducted questionnaire, they were split into two groups, i.e., Random and Induced. The former, comprising 542 members, attended the survey due to mere curiosity; the latter, comprising 500 members, had individual reasons to participate, 72% claiming to have consanguineous family thyroid disease carriers, while the remaining 28% adduced a variety of causes (obesity, goiter suspicion and/or neck complaints, asthenia, dermatological or gynecological history, among others).
Results
Given the differences found between the Random and Induced Groups, and taking into account that due to their origin they should be considered separately, results achieved will be analyzed individually for each group. It should be pointed out that there were no differences in the quality and type of palpation performed by the physicians in charge of this task, so that no distinctions are made.
Random Group
Out of the 542 subjects making up this group, there were 455 (83.9%) women and 87 (16.1%) men. Women’s ages ranged from 2 to 83 years, while men’s ranged from 5 to 85 years. Age distribution in the female and male gender is shown in Figure 1.
Total goiter percentage was 8.7%, reaching 9.5% for women and 2.3% for men, with a 4.1:1 female:male ratio. Had male and female populations been distributed according to the masculinity index (number of men per 100 women) that the INDEC (National Institute of Statistics and Censuses) has calculated to be 91.6 for the population of the Metropolitan Area of Buenos Aires (2001 National Population, Homes and Housings Census)1, the goiter percentage would have been 6% (Fig. 2).
Fig 2.- Goiter prevalence in the Random Group, considered globally
(total observed) or discriminated by sex. The calculated total * refers to
the application on the observed total of the masculinity index, established
by the INDEC for the general population of the metropolitan Buenos Aires
area (see text).
When an attempt was made to correlate goiter frequency with
patient age, and in order to assemble an appropriate number of individuals to
allow reliable statistical analysis, it was decided to take men and women as a
whole and split them into two groups: older and younger than 40 years of age.
Thus, 175 individuals proved to be from 2 to 40 years old and 367 from 41 to 85
years. Goiter percentages were 9.7% for the younger and 7.9% for the older one.
However, statistical analysis carried out by the chi square method failed to
disclose any significant difference.
According to the criteria adopted in palpation guidelines (Table
1), 57.5% of goiters was exclusively diffuse and 42.5% belonged to some nodular
goiter variant. With regard to the latter, only a quarter were single solitary
nodules in a thyroid gland which, except for the nodule, was clinically normal.
Figure 3 shows the frequency of each goiter variant in the
Random Group and the hypothetical value in the general population (once values
were extrapolated according to the INDEC masculinity index). Thus, the percentage
of palpable nodules in the general population of Buenos Aires City and its surroundings
area proved to be 2.5%.
Fig. 3.- Prevalence of goiter variants in the Random Group. Abbreviations
are explained in Table 1. The General Population was taken as the same Random
Group, after correcting for the INDEC masculinity index (see text).
The ages of patients with palpable thyroid nodules ranged from 21 and 82 years, while those of subjects with diffuse goiter had a range from 16 to 65 years. Overall, 90.5% of nodular goiter was observed in patients over 40 years of age, among whom only 42.3% diffuse goiter was found. When the prevalence of nodular goiter was calculated as a function of age, there was a definite increase with more advanced age (Fig. 4). Younger individuals (up to 40 years of age) had a 1.2% frequency of thyroid nodules, but those over 40 years of age reached, as a group, 4.6% of nodular goiter. In contrast, the prevalence of diffuse goiter was lower in elder subjects, reaching 8.8% in the younger group and 3.0% in the one over 40 years of age.
Fig. 4.- Prevalence of thyroid nodules in Random group individuals subdivided
according to ages.
Induced Group
With a total of 500 individuals, this group comprised 453 women
(90.6%) and 47 men (9.4%). Female ages ranged from 2 to 82 years, and male ones
from 3 to 83 years. The age distribution of women and men is shown in Figure
1. The total percentage of goiter was 14.4%, reaching 15.5% for women and
4.3% for men. Male: female goiter ratio was 3.6: 1, slightly smaller than that
of the Random Group. The greater goiter prevalence in the Induced Group, compared
with that of the Random Group, proved statistically significant in the chi
square test (p<0.005).
Among individuals over 40 years of age, goiter prevalence was
13.4%, while in the younger group it reached 14.6%, a difference lacking
statistical significance. None of the Induced Group individuals presented
multinodular goiter, exclusively diffuse goiter proving the most frequent
variant (73.6%), followed by solitary nodules in normal thyroid (20.8%) and,
finally, by single nodules in diffuse goiters (5.6%). The frequency of each
goiter variant in the total Induced Group population were as follow: 10.6% for
diffuse goiter, 3% for solitary nodules and 0.8% for nodules that appears in
the context of a diffuse goiter. As in the Random Group, the prevalence of
thyroid nodules was substantially higher in patients over 40 years of age, this
subgroup comprising 89.5% of cases. A 26-year-old patient presented, besides a
diffuse goiter, a thyroglossal cyst.
When the Induced Group was split into two populations with and
without a family history of thyroid disease, it was observed that goiter
percentage was 13.1% for the former and 17.8% for the latter. Although failing
to reach significance level (p=0.06), this differential trend could end up by
becoming meaningful with a larger number of individuals. The reason for
consultation of subjects without a family history of thyroid pathology was
varied. Table 2 lists the causes reported by these individuals to attend the
goiter detection campaign.
TABLE 2.- Reasons
for consultation of the Induced Group patients who had no family history
of thyroid disease
Discussion
The epidemiology of goiter remains a relevant issue in areas
where inhabitants suffer an environmental deficit of iodine. For more than
three decades, Law 17259/67 compels Argentine salt companies to iodize salt for
human and animal consumption throughout the national territory2. The metropolitan area of Buenos Aires
never had a severe lack of iodine prior to the compulsive use of iodized salt3. However, an epidemiological survey
conducted in Buenos Aires before establishing prophylactic measures found a 14.8%
goiter prevalence4. Starting
from 1970, it became a region where iodine deficiency disappeared5,
presenting an average urinary iodine excretion of roughly 200 µg/day6
and goiter prevalence decreased to 8.5%4.
Thus, the present campaign of goiter detection affords the opportunity to
determine its prevalence regardless of the variations that depend on dietary
iodine content. For such a reason, gleaning these epidemic, previously
unavailable data in our environment, was part of the main goals that prompted
us to organize the so-called Thyroid Survey Week.
As widely recognized, goiter is the common denominator of many
thyroid disorders, and is present in nearly 90% of untreated thyroid pathology,
so that its detection encompasses a broad spectrum of thyroid diseases commonly
found in the general population. Perhaps, the only subgroup of autoimmune
thyroiditis that develops without goiter is a small part of its hypothyroid
variant7, proving the single
thyroid disorder that, in practice, is not detected in the monitoring modality
carried out in this campaign. Lastly, the rare cases of hyperthyroidism of the
elderly with normal thyroid palpation and, obviously, carriers of thyroid
incidentalomas, could be added to the group of non-goiter patients.
The division into two groups (Random and Induced) of the
examined individuals was intended to gain an accurate idea, on the one hand, of
what occurs in the general population not subjected to any bias and, on the
other, to discern the true extent of thyroid pathology in subjects who may be
classified as a population at risk. Therefore, it is quite reasonable to
observe differences in goiter prevalence between both groups (Fig.
5).
On analyzing their percentage in the Induced subgroup lacking a
family history of thyroid disease, as compared with the Random group, we
observed that goiter frequency proved two-fold. This finding is of considerable
interest because it supports the need to search for thyroid pathology in all
individuals consulting for other causes, but whose non-endocrinological
disorder may be related, either directly or indirectly, with thyroid gland
disease. Following this line of thought, our results also advocate monitoring
consanguineous family members of thyroid disease carriers, in whom a simple
neck palpation may prove relevant.
Fig. 5.- Goiter prevalence in each group, Random and Induced [black bars],
and in subgroups (with and without a family history of thyroid disease) of
the Induced Group [white bars].
In the worldwide literature, there are several reports on the
incidence and prevalence of goiter in the general population8-10. However, as far as we have been able
to ascertain, there are none available where an Induced population is compared
with one of a Random nature, as that carried out by us during the Thyroid
Survey Week. The classic United Kingdom Whickham survey8 disclosed that goiter prevalence
diminished with patient age, since a follow-up survey conducted 20 years after
the first one showed significantly lower frequencies. In 1993, the latter
report documented 10% frequency in women and 2% in men. These figures closely
tally with ours, as we recorded similar percentages of goiter in Random Group
subjects, i.e., 9.5% in women and 2.3% in men. In the Framingham study, Vander
et al.9 found a 4.2% prevalence
of palpable nodules in a population whose ages ranged from 30 to 59 years, in
comparison with our 2.5% figure for nodular pathology for the general
population (corrected by the INDEC masculinity index). However, such frequency
approached 4% in individuals comprised within the age slot from 41 to 60 years,
proving very similar for age-matched subjects of the Framingham study.
As well documented, the prevalence of nodules in a community
varies according to the methodology used for their detection. Thus, the
greatest frequency is observed in autopsy specimens (13-65%), followed by
echography (19-35%) and lastly by palpation (0.2-5.1%)10. In all likelihood, palpation performed
by experienced hands disclosed with greater certainty the group of nodules with
clinical relevance. Except for a minor percentage of incidentalomas, detected
by echography, the great majority proves no more than a simple finding of
doubtful significance.
As regards exclusively diffuse goiters, the cases that we have
seen should have been mostly in patients with thyroiditis. This statement is
based on the fact that autoimmune thyroid pathology is, in the adult, the most
common cause of diffuse enlargement of the thyroid gland7. Another cause of diffuse goiter is
simple goiter11. Quite likely,
these two pathologies were responsible for the almost entirety of the observed
diffuse goiters, except for a couple of cases of hyperthyroidism due to Graves’
disease that belonged to the Induced Group without a family history of thyroid
disease. It should be highlighted that one of these patients attended due to
menstrual alterations, while the other one did so due to palpitations. In both
cases, they related their symptoms with the thyroid through the press
information that one of us (H.N.) provided before television media to promote
the campaign. In a single case, also belonging to the Induced Group, a
thyroglossal cyst was detected in a carrier of a diffuse goiter. This finding
confirms the very low prevalence of these cysts in the general population12.
Wang and Crapo10
have pointed out that the prevalence of hidden thyroid cancer differs by two
logarithms when comparing it with clinically evident thyroid cancer, from which
they inferred that most hidden carcinomas never reach clinical relevance. In a
study carried out over a decade ago, while searching for the incidence of
thyroid cancer in the metropolitan area of Buenos Aires, we found that this was
one of 35 new cases per million inhabitants per year13. Bearing in mind that the statistical
probability that a thyroid nodule should be cancerous is nearly 5%14,
in the present study, where we recorded 2.5% of nodules in the general population,
perhaps only one out of every 3 or 4 palpable malignant neoplasic nodules are
finally diagnosed as such. The query posed is therefore: What happens to the
other 2 or 3? Although the answer is uncertain, it is reasonable to believe that
such patients would hardly ever experience any outcome attributable to those
tumors.
Interestingly, within the Induced Group, a slightly higher
frequency of goiter was disclosed in subjects lacking a family history of
thyroid disease, when compared to those with such a history. Perhaps the explanation
is that such subgroup had a greater risk for the type of ailments that prompted
them to participate in the goiter detection campaign.
Another absorbing finding of our study arises from the
observation that the percentage of solitary nodules, in glands apparently
normal to palpation, proved three-fold higher in the Induced Group as compared
to the Random Group (3.0% vs. 0.9%). In a recent report15, we have stressed that follicular
adenomas present a greater risk of developing in glands affected by thyroid
au-toimmunity than in absolutely normal glands. In that work, we only studied
adenomas presenting as single nodules in an apparently normal thyroid. Assuming
that Induced Group patients probably have a greater frequency of thyroid
autoimmunity than those in the Random Group, it may readily be inferred that
findings from both studies would bear a logical inter-correlation.
To sum up, it may be stated that the"Thyroid Survey Week"
campaign rendered valuable information to discern the status of goiter among
the inhabitants of Buenos Aires metropolitan area, disclosing significant
differences between Random and Induced Group individuals. Furthermore, given
the paucity of available data on the epidemiology of goiter in this South
American population, these results are useful to build the world map of goiter
prevalence in non-endemic areas. Moreover, such data support the recommendation
that thyroid palpation should be included in the clinical examination of all
patients, regardless of the specialty of the attending physician. Although
palpation, even when performed by the highly skilled, lacks the sensitivity of
ultrasound in searching for small nodules, it still affords the advantage of
negligible economic cost and, when carried out by expert hands, is able to
detect most of the clinically relevant thyroid pathology.
Acknowledgements: The Thyroid Survey Week enjoyed the valuable collaboration of the following physicians of the Endocrinology Division of the Hospital de Clínicas"José de San Martin": Silvia Guaita, Javier Herrera, Analía Pignatta, Efraín Salvioli, Liliana Santángelo, Magdalena Uhart and Sabrina Lucas. The following medical undergraduates also lent efficient aid: Paola Avila, Mónica Poggi, Melina Mastropietro, Sheila Jara Aguin, Silvia Salacz, Jaime García, Pablo Grana, Cecilia Martin, Gustavo Werber and Mariela Brugnolo. Likewise, we are indebted to the Hospital Press Office, that had the responsibility of divulgement to the public and information media, besides collaborating actively in logistical tasks of the campaign.
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Received: 11-03-2003
Accepted: 4-09-2003