Endocrine Abstracts

A 25 year old gentleman was referred to the endocrine clinic for evaluation of abnormal thyroid function tests. He reported symptoms of diffuse abdominal pain associated with loose stool up to six times a day with urgency, frequency and tenesmus. These symptoms had been present since childhood, becoming increasingly troublesome over the preceding two years. He also reported symptoms of tiredness, palpitations and sweating episodes. Thyroid function tests were abnormal. TSH was 0.78 mU/l (reference range 0.27–4.2 mU/l) and Free T4 29.7 pmol/l (reference range 10.5–24.5 pmol/l). He had a family history of hypothyroidism on replacement thyroxine. On examination he was found to have a BMI of 24.6 kg/m². His blood pressure was 156/96 mmHg with a regular pulse rate of 96 bpm. He demonstrated a fine tremor but lid lag was not detected. There were no thyroid masses felt with in the neck. His abdomen was diffusely tender, more intensely so in the left iliac fossa. Visual fields were full to confrontation and fundoscopy was normal. There was no clinical concern regarding pituitary enlargement. Repeat thyroid function tests confirmed Free T4 36.0 pmol/l, Free T3 10.4 pmol/l (reference range 3.1–6.8 pmol/l) and TSH 1.33 mUl/l. Haematology and biochemistry was unremarkable other than a microcytosis and slightly raised ALT. He was started on Carbimazole 20 mg once daily in Primary Care but this failed to improve his symptoms and this medication was stopped following Endocrine review. In view of his persistently high blood pressure, symptoms of anxiety and increased bowel frequency, Phaeochromocytoma, Conns Syndrome and Carcinoid Syndrome were excluded. The remaining 0900 h pituitary profile was normal. Extensive investigations including MRI abdomen, colonoscopy and biopsy and faecal calprotectin did not find a conclusive cause for his abdominal symptoms. In view of the persistently measurable TSH in the context of raised free T4 and T3 levels, Thyroid Hormone Resistance was suspected. Genetic studies confirmed Heterozygous THRβ pathogenic variant and confirmed the diagnosis of thyroid hormone resistance and he was started on Propranolol with normalisation of blood pressure and resolution of symptoms of tachycardia and palpitations. He continues to complain of symptoms of diarrhoea and intermittent abdominal discomfort and we wonder these symptoms may be related to raised FT4 levels.