Thyrotoxicosis in an Elderly Patient Simulating Infectious Gastroenteritis

Thyrotoxicosis in an Elderly Patient Simulating Infectious Gastroenteritis Moe TO1*, Htwe TH2, Yin TA3 and Ani T2 1Department of Geriatric Medicine and General Internal Medicine, Sandwell and West Birmingham Hospitals NHS, Birmingham, UK 2Department of General Internal Medicine, Heart of England NHS, Birmingham, UK 3Department of Respiratory Medicine, Doncaster Royal Infirmary, Doncaster and Bassetlaw Hospitals NHS, UK


Introduction
Thyroid disorders are common medical problems in older people, especially women. The thyroid disorders include overt and subclinical hypo/hyperthyroidism, sick euthyroid syndrome, goitres, thyroid carcinoma, apathetic hyperthyroidism [1]. In older people clinical features of thyroid disorders could sometimes not be clear and straightforward. Age-related physiological changes in the endocrine system, existing co-morbidities and polypharmacy might cause complexity in diagnosing underlying thyroid illnesses.

Case History
88 years old woman presented acutely with 10 days history of diarrhoea, nausea, and vomiting. She suffered about 6-7 episodes of loose stool everyday. Her diarrhoea was a watery, loose stool without having any blood or mucus. She had vomited 2-3 times everyday, associating with nauseous feeling. Neither coffee coloured granules nor blood was noticed in her vomit. In addition to above symptoms, her complaint of intermittent, colicky type pain below umbilicus. Her subjective pain score was 6 out of 10. She was also very lethargic and had loss of appetite. Her background medical history included type II diabetes mellitus, TIA (transient ischaemic attack), gastro-oesophageal reflux, osteoarthritis and hypertension. Her medications included Gliclazide 80 mg OD, Metformin 1g BD, Bendroflumethiazide 2.5 mg OD, Amlodipine 10 mg OD, Paracetamol 1g QDS, Lansoprazole 30 mg OD and Aspirin 75 mg OD.

Abstract
A case of "apathetic" hyperthyroidism in which an elderly lady presented with symptoms of gastroenteritis was described. Thorough clinical assessment and systematic diagnostic work up are imperative to confirm an occult thyroid disorder as undiagnosed thyroid illness could cause a variety of adverse outcomes in old age.
Differential diagnoses were considered as The initial management included fluid replacement with electrolytes correction, withholding of all anti-hypertensives, Lansoprazole, Gliclazide and a reduction of the dose of Metformin (500 mg BD).
Having diagnosed autoimmune thyrotoxicosis (Graves' disease), she was treated with oral Carbimazole 20 mg OD, intravenous Hydrocortisone 200 mg stat followed by 100 mg TDS for 3 days. All her symptoms were settled with overall clinical improvements within three days. Her electrolyte imbalances were also completely corrected. In the follow-up clinic four weeks later she returned to her normal activities with resulting in significant improvements of TFT. Her Carbimazole dose was gradually tailed off from 20 to 10 mg and then to 5 mg with serial monitoring of TFT and clinical assessment.
should be considered infective until proven otherwise. The aging process influences homeostatic mechanisms, making the elderly more susceptible to enteric pathogens [3]. A clear history and appropriate investigations should identify the causative organism. Negative stool cultures and PCR for viral pathogens should lead to consideration of other diagnoses.
As in our patient's presentations hyperthyroidism in old age can present with non-specific vague symptoms such as nausea, vomiting, lethargy, fatigue [4,5]. This form of hyperthyroidism is known as "Apathetic" or non-activated hyperthyroidism [4,5]. It is principally found in the elderly population and the usual hyperkinetic presentation of thyrotoxicosis is replaced by apathy and inactivity, making it difficult to diagnose [6]. Untreated hyperthyroid state increases risks of angina, heart failure and atrial fibrillation in the elderly [4]. Osteoporosis could occur as a result of increased bone turnover [4].
There are different causes of hyperthyroidism. Among these causes Graves' disease (autoimmune) is the most common cause of hyperthyroidism. Raised free T4 or T3, low TSH and presence of thyroglobulin antibodies could confirm the diagnosis of Garves' disease [4,7,8].
Management of hyperthyroidism comprises three main stays of management; drugs therapy, surgery and radioactive iodine treatment [5]. Surgery is not a popular choice in older patients as these patients usually have multiple co-morbidities and present as high risk for operation [5]. Either drug therapy or radioactive iodine treatment is favourable [5]. If drug therapy is chosen, Propylthiouracil 200-400 mg or Carbimazole 20-40 mg (once daily or divided dose) is used as initial treatment [4]. This initital treatment should be continued until an euthyroid state is established, which can take 4-8 weeks to reach [4]. Therefore, TFTs should be repeated in 2-4 weeks time after introducing the initial treatment [4]. After achieving an euthyroid state, two main treatment options should be considered; titration regimen (antithyroid dose is gradually reduced to a maintenance dose of Carbimazole 5-15 mg or Propylthiouracil 50-150 mg daily with continued monitoring of TFTs) or block and replacement regimen (High dose antithyroid is continued to switch off thyroid synthetic function completely and levothyroxine is commenced promptly when free T4 level is supressed) [4]. Drug sideeffects of carbimazole include agranulocytosis and propylthiouracil can cause hepatotoxicity [4,7]. Beta-blockers are indicated only for controlling symptoms such as symptomatic tachycardia [5]. A short course of systemic steroids could be administered if patients are in an acute phase of hyperthyroidism or a thyroid crisis [8].
In our patient Carbimazole 20 mg was initially introduced following a titration regimen as above. She had well tolerated to the treatment and did not present any side effect of the drug.

Conclusion
This case clearly reminds us that hyperthyroidism should be considered as an important differential diagnosis if an elderly patient presents with vague non-specific symptoms. Acute diarrhoea is uncommon in apathetic hyperthyroidism whilst infectious gastroenteritis remains the most common cause and should be excluded before alternative diagnoses are sought.