Dr Broda O Barnes, who studied thyroid disease for 35 years, believed that many people have subtle thryoid disorders that don't show up on a blood test.

She championed a simple, and accurate home test for hypo or hyperthyroidism by recording the BBT the lowest temperature that you achieve during the day. As you wake up (before rising or drinking tea), place a thermometer under your armpit for 10 minutes.The supposedly normal readings are between 36.6¡C to 36.8¡C (97.8¡F to 98.2¡F). Anything lower could be an underactive thyroid and anything above, a hyperactive one.

If you're a premenopausal woman, the most accurate measurement is on days two or three of your menstrual cycle; otherwise, the BBT will slightly rise and fall just before and after ovulation. (If you've passed the menopause, recording your temperature on any day is fine.)

Nevertheless, any such test, including BBT, is no substitute for careful consideration of your entire, individual clinical picture. The main symptom is either irritability and agitation and unexplained weight loss in the case of hyperthyroidism and a general slowing of mental and physical function tiredness, weight gain, lack of ability to concentrate if you are hypothyroid.

It's also important to have your endocrine system checked out. Because TSH and your sex hormones are regulated by the pituitary, women with unbalanced hormones often have thyroid problems as well.

Sorting out the hormone imbalance often corrects the thyroid problem.