People with Down syndrome tend to have more medical pathology than the general population, including thyroid disease. The prevalence of thyroid dysfunction in the Down syndrome population varies among different studies, depending on the sample size, the population chosen and the diagnostic criteria used. Hypothyroidism is the most frequent form of thyroid dysfunction in people with Down syndrome and its prevalence ranges between 30 and 40%.
Hyperthyroidism also occurs more frequently in patients with Down syndrome although in a lower proportion than hypothyroidism.
Case series: hyperthyroidism in Down’s syndrome
In this study we performed a systematic review of 1,832 patients seen at the Fundació Catalana Síndrome de Down (FCSD) between 1991 and 2006, and identified all patients in the database with hyperthyroidism. The following variables were collected from these patients: age, anthropometric measurements, clinical characteristics (palpitations, insomnia, heat intolerance, sweating, nervousness, increased stool habit, distal tremor and weight loss), physical examination and laboratory tests. Family history of disease was also recorded, as well as the presence of other autoimmune disorders. Moreover, a tenetium-99 scan was also performed in all patients, in addition to a bimonthly follow-up throughout the study.
Results
After the study it was concluded that, of the 1,832 patients with Down’s syndrome attended, 12 were diagnosed with hyperthyroidism. The mean age of the patients was 16.8 years, mean weight 42.5 kg and mean height 142.6 cm. Six months after starting treatment, there was a mean weight gain of 11.4 kg and a height gain of 5.3 cm. As for the symptoms of hyperthyroidism, at the time of diagnosis:
- 11 of the patients had heat intolerance and excessive sweating.
- 10 had increased irritability
- 10 had suffered weight loss in the previous months
- 9 had palpitations
- 7 had insomnia
- 7 had distal tremor
- 4 had increased stool rhythm
- 3 noted eye irritation
Moreover, tenetium-99 scintigraphy showed a diffuse hyperenhancement in all patients, which led to a diagnosis of Graves-Basedow disease.
Treatment for hyperthyroidism
Following the diagnosis of hyperthyroidism, treatment was initiated with carbimazole, a treatment that inhibits thyroid hormone synthesis. It was administered in all patients at a dose of 10 mg three times a day. Afterwards, the total daily dose was adjusted according to periodic analytical determinations, until a definitive treatment was established.
Conclusions
Based on the results of this study, we can conclude that, within the thyroid pathology of Down syndrome, hyperthyroidism is less frequent than hypothyroidism and that the etiology in most cases is Graves’ disease. The impact it may have on growth and pubertal development must be taken into account. Early diagnosis and treatment is important, but annual biochemical screening is not useful. Therefore, clinical suspicion is essential to reach the diagnosis of the disease relatively quickly. Spontaneous remission is rare and definitive treatment is usually necessary in almost all cases.