Speech language pathology disorders in children with congenital hypothyroidism: critic review of literature

Abstracts

Congenital Hypothyroidism (CH) is the most common congenital endocrine disorder in childhood which corresponds to a deficiency of thyroid hormones. This article aimed to do a literature review about the Speech Language Pathology disorders that might be associated to HC. The keywords used for searching the electronic databases PUBMED and MEDLINE were: congenital hypothyroidism OR hypothyroidism AND hearing OR voice OR language. It was included studies published up to July 2011. Two researchers did the analyses, independently, with further discussion and consensus about the inclusion. Out of the 324 studies found in the preliminary analysis, only 20 of them were included in the final sample after establishing the criteria for inclusion. We observed that a great number of articles on the children language development on CH, but controversial ones, when it comes to the results of the evaluations. In Audiology, there has been a reduction in the number of articles that describe hearing loss in children who had CH. Only two papers were found about the voice, which referred exclusively to crying abnormalities in babies affected by CH. Although some findings were proven relevant to the subject, the great variability of the research methodology does not allow us to have a clear conclusion on the probable speech language pathology disorders in children with congenital hypothyroidism.

Congenital Hypothyroidism; Speech, Language and Hearing Sciences; Child; Hearing; Voice; Language

O Hipotireoidismo Congênito (HC) é a doença endócrina congênita mais comum na infância e corresponde à deficiência de hormônios tireoidianos. Este artigo teve o objetivo de realizar uma revisão crítica da literatura, a respeito das possíveis alterações fonoaudiológicas relacionadas ao HC. Os descritores utilizados para a busca nas bases de dados eletrônicas PUBMED e MEDLINE foram: hypothyroidism OR congenital hypothyroidism AND voice OR hearing OR language. Foram incluídos estudos publicados até julho de 2011. As análises foram realizadas independentemente por dois dos pesquisadores, com posterior discussão e consenso sobre a inclusão. Dos 324 estudos localizados na análise inicial, apenas 20 compuseram a amostra final após o estabelecimento dos critérios de inclusão. Observou-se que há um número considerável de artigos sobre a linguagem de crianças com HC, embora com controvérsias no que se refere aos resultados das avaliações. Quanto à Audiologia, nos últimos anos houve uma redução no número de artigos que descrevem alterações auditivas em crianças com HC. Na área de Voz, foram localizados apenas dois artigos, que se referiram exclusivamente às anormalidades observadas no choro de bebês com HC. Embora com algumas constatações relevantes a respeito do assunto, a grande variabilidade metodológica das pesquisas não permite que se tenha uma conclusão clara sobre as possíveis alterações fonoaudiológicas em crianças portadoras de hipotireoidismo congênito na atualidade.

Hipotireoidismo Congênito; Fonoaudiologia; Criança; Audição; Voz; Linguagem

Introduction

Congenital Hypothyroidism (CH) is the most common endocrine congenital disease in childhood and its incidence is one for each 3000 up to 4000 births. Characterized by the lack of thyroid hormones (TH), CH may be prematurely detected through newborn screening test (the neonatal heel prick). Thyroid gland is responsible to produce, to store, and to release the TH (thyroxine and triiodothyronine) in bloodstream. The HT acts in almost all the organism cells in enzymatic concentration and activity, in substrate metabolism, as vitamins and minerals, basal metabolism, and also stimulates the oxygen absorption¹.

In fetus and newborn (NB) the TH are determinant to central nervous system (CNS) development. In case of improper or premature hormone restoration the growth and development sequels may be irreversible².

Literature reports the presence of speech-language disturbances in CH children. Studies point out the language disorders associated to CNS³ development disturbances, and hearing losses due to maturation dysfunction of inner ear structures and VIII cranial nerve myelination⁴. Regarding voice, the rough crying is the one of clinical symptoms common at birth⁵, which may occur up to 20% of cases⁶. However the scientific evidences are not clear yet, especially about the endurance of this symptom during first childhood in premature treated children.

It is believed that the speech-language disturbances related to language, hearing and voice must be investigated mainly due to the advance in newborn screening tests systems and follow-up. It is possible that diagnose and premature treatment may be related to decreasing negative consequences to children.

The purpose of the present study was to review the literature regarding possible speech-language disturbances related to congenital hypothyroidism and, therefore, to answer the following question: "Is there scientific evidence about the presence of speech-language disturbances in children with congenital hypothyroidism?"

Methods

The papers search was done in PUBMED and MEDLINE electronic database during 2011 July. The used keywords to search were: hypothyroidism OR congenital hypothyroidism AND voice OR hearing OR language. The crossing among all keywords combination was made.

The papers search process was done by two of the researchers of the present research, individual and independently, to posterior comparing and defining the final sample inclusion. To all data collection steps, the results of each researcher were compared and, at the end of each step, a meeting to consensus and clearing possible conflicts/inconsistencies regarding the found papers was made.

The inclusion criteria were: papers related to voice (phonation and resonance), language and hearing in children with congenital hypothyroidism (primary); with evidence level 1 (systematic review), 2 (controlled random studies), or 3 (nonrandomized studies), according to the proposed classification in previous study⁷; published up to 2011 July. The exclusion criteria were: papers which theme were not direct related to the speech-language aspects; written in other languages than English or Portuguese; which themes were acquired or transitional hypothyroidism; in which the congenital hypothyroidism were associated to others diseases/comorbidity; which abstracts were not able to be accessed in included database (PUBMED and MEDLINE) or CAPES periodic homepage; about adults exclusively; and using animal model.

At first, 324 papers about speech-language pathology and the diverse types of thyroid disturbances were located. Through title analysis, 100 were selected having direct relation to this review theme. 47 papers were excluded since they were coincident at both databases. Finally, eight papers were excluded since they were published in other languages than English or Portuguese, and therefore, the abstract and the complete text were not available in either the two languages. Thus, 45 papers remained to the next review step.

At second step, it was verified the abstracts existence. 13 papers were excluded since they did not have the abstract available at the website of the included databases (PUBMED and MEDLINE) and/or at CAPES periodic homepage and, therefore, the content of the paper could not be evaluated. Thereby 32 papers remained, 20 of them were accessed through CAPES periodic homepage, 11 were requested to national libraries, and one to an international library. Through reading the abstracts and full papers there was the exclusion of 12 papers due to not being compatible to the study theme. Therefore, the final number of papers included in the sample was 20 (Figure 1).

Figure 1:
Flowchart about data collection

It was made a descriptive analysis about the content of the included papers in this review. It was sought to observe agreement and disagreement points among them, besides to identify whether there were enough scientific evidence to draw the speech-language pathology profile of CH children.

It was collected data regarding research purpose, age range, presence of control group, and main obtained results. From that, compiling data and critic analysis were made.

Literature review

The following results were distributed according to Speech-language pathology researched fields. It was located seven papers in Audiology, 11 in Language, and two in Voice (Figure 2)

Figure 2:
Contents of localized papers about speech-language disturbances related to congenital hypothyroidism

Regarding Audiology, excepting one literature review paper⁸, which was made the option to include in the sample due its precursor character in investigating hearing losses due to congenital hypothyroidism, the others papers (n=6) ^{9 - 14} are transversal studies. Most of them^{10 - 13} were carried out in the nineties. From the total papers which reported the possibility of hearing loss in CH children^{9 , 12 , 13}, only one of them had more methodological strength, having control group and a considerable number of children (n=75) ¹³. The other papers, as the ones with newborns^{10 , 14} as with children¹¹, did not prove the relation between congenital hypothyroidism and hearing loss.

The papers located were about peripheral auditory evaluation. It was not located specific papers about the hearing processing investigation, defined as mechanisms and process of auditory nervous system, which promotes speech decoding and comprehension, especially in unfavorable situations, as the background noise presence or competitive speech¹⁵. It is considered of major importance to carry out new researches that investigate this aspect. It is believed that the results of these researches may contribute to clearing other complaint types commonly reported by the CH children, in language and learning (school, attention, memory and others difficulties).

Besides, the hearing loss incidence in CH children is questionable, since none reviewed paper had epidemiologic character. The only paper⁹ suggesting hearing deviations percentage (10% or a tenth) to this population have a big variability regarding the beginning of treatment of the participants (14 days to seven years and three months), which could possible question and generate bias of the obtained results.

The results showed from the three Speech-language Pathology fields investigated, language was the one with higher number of published papers^{16 - 26}. This allows the arguing about this topic in CH children to be more clear and consistent, but do not exclude the importance of other communication aspects. It is worthy to note that the totality of found papers corresponds to oral language deviations, with only two paper having information about writing language, literacy process, and scholar development in CH children.

Besides, about language yet, it was observed the predominance of cognitive process focus, with complementary information about the deviations in this area. Therefore, QI information, memory, attention skill and general neuropsychological development overlapped specific language data, with the contribution of these aspects regarding the language disturbance not clear.

About the content of the language files papers, there are still controversies about the relation between its development and CH presence. Some papers report proper development when CH children are compared to control children^{16 , 21 , 25}. On the other hand, other studies point out phonologic deficits and significant delay in language development^{17 - 20 , 22 - 24 , 26}. Lower inconsistencies were observed when the language deviations were related to CH etiology and "severity of the disease at diagnose (newborn screening)" variables. All the papers that purposed to evaluate such relation concluded that thyroid agenesis and more deviated hormone levels at diagnose (more severe) contributes to a higher risk to deviation in language development^{17 - 19 ; 23 , 24}.

There was a big methodological variability in Language papers, probably due to the differences and particularities regarding main evaluation focus (some papers includes the language evaluation as complementary to neuropsychological development evaluation), or the academic graduation and research line of the author(s). Besides, does not seem to have a relation between the paper publication period and obtained results, once the most recent ones had variability about the findings of CH children language development^{22 - 26}.

About the relation between congenital hypothyroidism and possible vocal deviation in children, there still is a big gap of knowledge to be fulfilled. That is because, even the literature pointing out rough cry as one of the main clinic symptoms of CH children at birth (usually evaluated under the physician perspective), only two papers made objective analysis about the subject^{27 , 28}. The two papers have similar conclusions and make clear there is a considerable level of CH newborns having voice deviations. One of them²⁸ points out that even after a month treatment and the hormone levels within normal patterns, part of the children still had vocal disturbances. However, there was not obtained papers that pointed out any evidence about the maintenance of these deviations throughout first childhood. It is worthy to mention that one of the above mentioned researches²⁸ is from the medical field and it was carried out trying to relate vocal characteristics to neurologic and breathing development of the children²⁸. But it was made the option to select the paper to this review due to acoustic analysis inclusion and the shortage of papers with strong data about the topic.

It was not located other studies of voice assessment in CH children, in any other age range than newborns. So, it is important to carry out other researches that clear this aspect, once there is still not clear whether there is the maintenance of a possible dysphonia throughout childhood information.

Currently, with the advance of newborn screening programs, the CH newborns receive treatment and medical attendance since the first weeks of life. The hormone reposition and following will be permanent which may promote the normal or very close to normality growth and development. However, the real implications of prematurely treated CH, mainly in teenage and adulthood, are still unknown²⁹. Therefore, longitudinal studies, which will follow the hearing, language and voice development, are fundamental in order to better understand the cases progress and their hypothyroidism possible consequences with aging. It is worthy to highlight that newborn screening became a law in Brazil in 1990 and 2001, through GM/MS ordinance nº 822, and it was held in all national territory and, therefore, there are already a big number of teenagers and adults followed since their birth, systematically, in specialized centre³⁰.

Conclusion

The big method variability of the reviewed papers does not allow a clear conclusion about possible speech-language disturbances in children having congenial hypothyroidism, mainly in Audiology and Voice fields. Some papers, really old, report the subject in a previous moment to newborn screening tests implantation which certainly contributed to the bigger number of descriptions in the children of these researches. Although it seems to have a tendency to "normalization" or decreasing the number of speech-language disturbances as the screening tests implantation happens, there is a lack of evidence regarding the subject.

It is important that new researches in language to be performed by speech-language pathologists in order to be possible to prior and analyze the most important aspects of the field, adding the speech-language pathology perspective so the findings may be easily applied in human communication disorders clinic. The audiology researches have been prioritized only audiometric thresholds and, therefore, researches about sound perception should be carried out. In voice, the production is pretty scarce and, even coinciding about deviations in voice of CH newborns they do not allow to make inference about possible dysphonia maintenance in childhood and teenage.

Speech-language pathologist action in congenital hypothyroidism children is still poorly discussed and deserves attention. Therefore, the insertion of this professional in inter-disciplinary teams that follows CH children should be considered, and also in the development of researches that produce stronger evidence regarding the importance of its action to this population.

Acknowledgment

We would like to thanks the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) the financial support in order to perform this research through scholarship master and doctoral grants to the first and second authors, respectively.

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• Financial source: CAPES

Publication Dates

• Publication in this collection
  nov-dec 2014

History

• Received
  11 July 2013
• Accepted
  28 Jan 2014