Endocrine Abstracts

A 37 year-old gentleman presented following an episode of dizziness while at work operating a fork-lift truck. There was no collapse or associated symptoms. He had been diagnosed with autoimmune hypothyroidism two months previously; commenced levothyroxine, currently at a dose of 75 micrograms daily; and lost ten kilograms in weight. On examination there were no signs of hypoadrenalism aside from a significant postural drop in blood pressure (lying 139/77 mmHg, standing 115/76 mmHg). Biochemistry was typical of hypoadrenalism with serum sodium 130 mmol/l, potassium 5.7 mmol/l and bicarbonate 20 mmol/l. Adjusted calcium was 2.46 mmol/l and renal function stable. Thyroid function tests showed TSH 0.32 mU/l and free T4 14.3 pmol/l. Short synacthen test results revealed cortisol 23 nmol/l at baseline, 24 nmol/l at 30 minutes and 25 nmol/l at 60 minutes. He was commenced on hydrocortisone 20 mg in the morning and 10 mg in the evening with fludrocortisone 50 micrograms daily. ACTH was later reported at 1067 ng/l and adrenal antibodies were positive, confirming Addison’s disease. The patient remained lethargic and computed tomography demonstrated a small thymoma. Acetylcholine antibodies were negative and the cardiothoracic surgeons felt no intervention was required. TSH remained mildly elevated with strongly positive thyroid peroxidase antibodies so levothyroxine was re-introduced with good clinical improvement. While studies have shown an increased risk of Addison’s disease with Hashimoto’s thyroiditis when compared to described background prevalence rates (Boelaert et al, 2010); interestingly a recent review of 3069 Caucasian patients with autoimmune hypothyroidism demonstrated only a near-significant association with Addison’s disease when compared with age- and sex- matched controls (Fallahi et al, 2016). 50% of patients with Addison’s will present in adrenal crisis (Chakera & Vaidya, 2010), and other case reports describe significant weight loss in this situation (Choudry et al, 2009; Murray et al 2001). This case highlights the need to be aware of this relationship, and to consider hypoadrenalism when symptoms do not improve on levothyroxine replacement, particularly with significant weight loss.