Hyperthyroidism is a well established cause of atrial fibrillation (AF). Thyroid Stimulating Hormone-secreting pituitary tumours are rare causes of pituitary hyperthyroidism. Whilst pituitary causes of hyperthyroidism are much less common than primary thyroid pathology, establishing a clear aetiology is critical in minimising complications and providing appropriate treatment. Measuring Thyroid Stimulating Hormone (TSH) alone to screen for hyperthyroidism may be insufficient to appropriately evaluate the thyroid status in such cases.
A 63-year-old Caucasian man, previously fit and well, presented with a five-day history of shortness of breath associated with wheeze and dry cough. He denied symptoms of hyperthyroidism and his family, social and past history were unremarkable. Initial investigation was in keeping with a diagnosis of atrial fibrillation (AF) with fast ventricular response leading to cardiac decompensation.
TSH 6.2 (Normal Range = 0.40 ├óÔé¼ÔÇ£ 4.00 mU/L), Free T3 of 12.5 (4.00 ├óÔé¼ÔÇ£ 6.8 pmol/L) and Free T4 51(10├óÔé¼ÔÇ£30 pmol/L). Heterophilic antibodies were ruled out. Testosterone was elevated at 43.10 (Normal range: 10.00 ├óÔé¼ÔÇ£ 31.00 nmol/L) with an elevated FSH, 18.1 (1.0├óÔé¼ÔÇ£7.0 U/L) and elevated LH, 12.4 (1.0├óÔé¼ÔÇ£8.0 U/L). Growth Hormone, IGF-1 and prolactin were normal. MRI showed a 2.4 cm pituitary macroadenoma. Visual field tests showed a right inferotemporal defect.
While awaiting neurosurgical removal of the tumour, the patient was commenced on antithyroid medication (carbimazole) and maintained on this until successful trans-sphenoidal excision of the macroadenoma had been performed. AF persisted post-operatively, but was electrically cardioverted subsequently and he remains in sinus rhythm at twelve months follow-up off all treatment.
This case reiterates the need to evaluate thyroid function in all patients presenting with atrial fibrillation. TSH-secreting pituitary adenomas must be considered when evaluating the cause of hyperthyroidism. Early diagnosis and treatment of such adenomas is critical in reducing neurological and endocrine complications.
- Fuster V, Ryden LE, Cannom DS, Crijns HJ, Curtis AB, Ellenbogen KA, Halperin JL, Le Heuzey JY, Kay GN, Lowe JE, Olsson SB, Prystowsky EN, Tamargo JL, Wann S, Smith SC Jr, Jacobs AK, Adams CD, Anderson JL, Antman EM, Halperin JL, Hunt SA, Nishimura R, Ornato JP, Page RL, Riegel B, Priori SG, Blanc JJ, Budaj A, Camm AJ, Dean V, et al.: ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: full text: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 guidelines for the management of patients with atrial fibrillation) developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Europace 2006, 8:651-745.
- Gammage MD, Parle JV, Holder RL, Roberts LM, Hobbs FD, Wilson S, Sheppard MC, Franklyn JA: Association between serum free thyroxine concentration and atrial fibrillation. Arch Intern Med 2007, 167:928-934.
- Beck-Peccoz P, Persani L, Asteria C, Cortelazzi D, Borgato S, Mannavola D, Romoli R: Thyrotropin-secreting pituitary tumors in hyper- and hypothyroidism. Acta Med Austriaca 1996, 23:41-46.
- Beck-Peccoz P, Brucker-Davis F, Persani L, Smallridge RC, Weintraub BD: Thyrotropin-secreting pituitary tumors. Endocr Rev 1996, 17:610-638.
- Lim EM, Bhagat CI, Walsh J: Asymptomatic thyrotropin-secreting pituitary microadenoma. Intern Med J 2001, 31:428-429. 6. Thyroid Manager [http://www.thyroidmanager.org/Chapter13/ 13A-frame.htm]
- Bertholon-Gregoire M, Trouillas J, Guigard MP, Loras B, Tourniaire J: Mono- and plurihormonal thyrotropic pituitary adenomas: pathological, hormonal and clinical studies in 12 patients. Eur J Endocrinol 1999, 140:519-527.
- Busenbark LA, Cushnie SA: Effect of Graves' disease and methimazole on warfarin anticoagulation. Ann Pharmacother 2006, 40:1200-1203.
- Bucerius J, Joe AY, Palmedo H, Reinhardt MJ, Biersack HJ: Impact of short-term hypothyroidism on systemic anticoagulation in patients with thyroid cancer and coumarin therapy. Thyroid 2006, 16:369-374.