Complications

The complications of subclinical hyperthyroidism include:

• increased all cause mortality:
  • in patients aged over 60 and with a single low TSH level, the standardised mortality ratio was between 1.7 and 2.1 over the following five years
  • most of this effect was caused by increased death from cardiovascular disease
    
    
• increased risk of atrial fibrillation:
  • patients aged 60 or older who have a TSH <0.1 mU/L have a relative risk of atrial fibrillation at 10 yr follow-up of 3.1
    
    
• increased risk of Alzheimer's disease and dementia:
  • patients with a TSH <0.4 mU/L have a relative risk of dementia of 3.5
    
    
• increased risk of vertebral fractures:
  • the rate of vertebral fractures is 4.4 fold higher in patients with a TSH <0.1 mM/L compared to controls

Reference:

• 1) Parle, JV, Maisonneuve, P, et al. Prediction of all-cause and cardiovascular mortality in elderly people from one low serum thyrotropin result: a 10-year cohort study. Lancet, 358, 861-65.
• 2) Sawin, CT, Geller, A, Wolf, PA, et al. Low serum thyrotropin concentrations as a risk factor for atrial fibrillation in older persons. N Engl J Med 1994, 331, 1249-52.
• 3) Kalmijn, S, Hehta, KM, Pols, HAP, et al. Subclinical hyperthyroidism and the risk of dementia. The Rotterdam Study. Clin Endocrinol (Oxf). 2000, 53, 733-37.
• 4) Bauer, DC, Ettinger, et al. for the Study of Osteoporotic Fractures Research Group. Risk for fracture in women with low serum levels of thyroid-stimulating hormone. Ann Intern Med, 2001, 134, 561-68.