1. tolbutamine (Rastinon), for diabetes;
2. chlorpropamide (Diabinese), also for diabetes;
3. phenylbutazone (Butacote), for ankylosing spondylitis;
4. diazepam, Valium, for anxiety;
5. heparin, to prevent clotting in heart problems;
6. lithium (Priadel), to prevent relapse in psychiatric illness;
7. beta-blockers (e.g. Inderal), for high blood pressure;
8. salicylates, including aspirin (e.g. Disprin), a pain-killer;
9. steroids (e.g. prednisolone), for any severe physical reaction;
10. phenothiazines (e.g. Largactil), major tranquillizers;
11. amiloride (e.g. Moduretic) a water tablet;
12. androgens (e.g. testosterone), male sex hormone;
13. tamoxifen, an anti-oestrogen to ward off breast cancer;
14. sulphonamides, anti-bacterial drugs;
15. acetazolamide (Diamox), for glaucoma and fluid retention;
16. resorcinol (Anusol), used for piles;
17. PAS for tuberculosis.

The following medicines have a different effect.

1. phenytoin and related medicines – these anticonvulsants, used to control epilepsy, use up the thyroid hormones unusually quickly and this may cause a shortage;
2. carbamazepine (Tegretol) this anticonvulsant inhibits the release of T4 into the blood;
3. co-trimoxazole (Septrin) – for urinary infections, also inhibits the release of T4 into the blood;
4. levodopa (Sinemet) and bromocriptine (Parlodel) are both used for Parkinson’s disease and both stop the stimulating action of TSH, leading to T4 and T3 lack.

Medicines that appear to increase T4 and T3

1. oestrogen (in the contraceptive pill and HRT), provides more of the transport protein; it binds the thyroid hormone to the proteins in teh blood so that less may be actually used so you may find you need a different source of contraception

2. frusemide type water tablets (e.g. Lasix) by getting rid of fluid, make the blood more concentrated so there is more of the hormones per millilitre. This however doesn't mean there is more hormone to use as it is not actually working correclty

Medicines containing iodine

1. Amioarone (Cordarone X) causes thyroid problems in 6% of people taking it;
2. Cough medicines containing iodides – including over-the-counter preparations;
3. X-ray contrast media, given for instance for gall-bladder investigations;
4. Povidone skin antiseptic (Betadine) and tincture of iodine;
5. Multivitamins/multimineral health pills.