This study found nearly all patients with thyrotoxicosis are females and in the age of mid-forties. The most predominant cause of thyrotoxicosis was a multinodular toxic goiter. The most common symptoms and most common sign were palpitation and palpable thyroid, respectively. The most common arrhythmias detected on electrocardiography was sinus tachycardia and atrial fibrillation. Among those who had an echocardiographic examination, 40 % of them were diagnosed to have dilated cardiomyopathy. Regarding management, all patients received PTU as an anti-thyroid drug and almost all (96 %) of them also took beta-blockers.
In this study, the majority (89 %) of patients were females. The mean age at presentation was 45 years and those who were above 40 years accounted for 58.5 % of the cases. This is similar to a study done in Addis Ababa, in which 90 % of patients were females and patients above 40 years of age accounted for 59 % of the cases with a mean age of 43.1 years . Another study in Ghana also showed similar results where the mean age was 41.5 and most of the patients (87.8 %) were females .
In this study, the leading cause of thyrotoxicosis was a multinodular toxic goiter. This finding was similar to a study done in the North-Western part of Ethiopia, which reported 54.9 % of thyrotoxicosis cases due to toxic multinodular goiter . This is explained by the presence of unresolved iodine deficiency in Ethiopia with a prevalence of goiter that ranges from 35 % up to 70 % [21,22,23,24]. According to a recent study done in Ethiopia, more than half (57 %) of school children were found to have low urinary iodine levels . This problem of iodine deficiency has persisted in this country despite the availability of iodized salt .
The most common symptom of patients with thyrotoxicosis was palpitation which was present in 85.5 % of the patients followed by fatigue (69.0 %) and heat intolerance (59.0 %). Similarly, Addis Ababa’s study revealed palpitation and heat intolerance as the most common symptoms of patients with thyrotoxicosis . As well, a study done in South-Western Nigeria found palpitation and fatigue as the most common symptoms which occurred in 85.0 and 63.4 % of patients, respectively . A study done in France on 1240 patients also supported the above findings and reported palpitation followed by weakness as the most common clinical presentation of thyrotoxicosis .
The most common sign in our study was palpable thyroid (93.0 %) followed by tachycardia (43.0 %), exophthalmos (17.5 %), and tremor (17.5 %). According to Addis Ababa’s study, palpable thyroid (goiter) was also the commonest sign of thyrotoxicosis which was detected in 99 % of the cases. Congruently, the most common sign in Nigerian study was palpable thyroid and found in 97 % of the cases . On contrary, a study done in Maharashtra, India found tremor as the most common sign of thyrotoxicosis, in about 63.0 % of patients .
The most common arrhythmia detected on electrocardiography (ECG) was sinus tachycardia followed by atrial fibrillation and this finding goes parallel with several case studies on thyrotoxic cardiomyopathy [27,28,29]. This prevalence of atrial fibrillation on ECG of patients with thyrotoxicosis is also comparable to a study done in India where it was 28 % . The prevalence of dilated cardiomyopathy in our study (which is around 40 %) is higher compared to other studies where it is reported to be 1 % . Even taking the whole participants as a denominator, still, the prevalence is higher which is about 17.5 %. There are two main reasons for this higher prevalence. The first reason is the late presentation with a mean duration of goiter (i.e., anterior neck swelling) of about 13 years. This explanation is supported by a study done in England that found older age, male sex, and longstanding thyrotoxicosis as factors that increase the risk of dilated cardiomyopathy . The second reason is that echocardiography was done only for patients with signs and symptoms of thyrocardiac diseases. In this study, the factors significantly associated with dilated cardiomyopathy were atrial fibrillation and tachycardia. Thyroid storm was present in 6 % of this study participants. This figure is comparable to a national study done in Japan where it was 5.4 % .
In our study, PTU was the only thionamide used to treat thyrotoxicosis. This is similar to the study done in Addis Ababa, Ethiopia where almost all of the patients received PTU . This finding contradicts a survey done by members of the Endocrine Society (ES), American Thyroid Association (ATA), and American Association of Clinical Endocrinologists (AACE 6) where the most commonly used drug was methimazole (83.5 % of the cases) while the use of PTU was limited to 2.7 % . This change in trend towards methimazole use in the developed world is because methimazole is associated with a high rate of free T4 normalization and fewer side effects [16, 33]. But in developing countries like Ethiopia, methimazole is hardly available and almost all thyrotoxicosis cases are treated with PTU . Currently, the recommendation is to use methimazole as the first line anti-thyroid with an exception during pregnancy in which PTU is preferred because of rare reports of birth defects associated with methimazole . Additionally, in life-threatening conditions like thyroid storms, PTU is also preferred since it inhibits the conversion of T4 to T3 . However, PTU is not a good choice of drug in controlling severe forms of the disease because it has a poor adherence rate, and several adverse effects .
The interval of TSH follow up was > 3 months in 112(56 %) of the patients and it was against the recommendations by the American Association of Clinical Endocrinologists and the American Thyroid Association which recommend TSH determination every 4 to 6 weeks for all patients till normalization of TSH and T4 [32, 37]. The most common reasons not to do it based on the recommendation were limited availability of the investigation and financial constraints (more than half of the patients had a lower monthly income which is below 20 USD).
Strengths of the study
It is the first study to assess the pattern, clinical presentation, and management of thyrotoxicosis in Tigray and can serve as a baseline for future studies related to the current topic. It has also tried to assess many aspects of thyrotoxicosis by collecting primary data using a pre-tested and comprehensive questionnaire.
Limitations of the study
Echocardiography, electrocardiography, and cytology were not done for all patients. As a result, this study may not show the true prevalence of cytologic types and cardiac complications in patients with thyrotoxicosis. Due to infrequent TSH follow-up, this study did not address time to normalization of free T4 and TSH.