What I do know from reading various articles is that doping athletes do not take just one medication they take a number of medications; doping body-builders call it 'the stack'. You 'cycle' on and off various meds some enhance your performance some counter the side effects of those medications. Other meds are 'masking agents' that allow a doping athlete to pass a dope test.
Recently a number of athletes have been caught and had their bans mitigated in return for cooperation, this cooperation I assume, would include information about the meds they are taking and why. It is possible that these anti-doping bodies have information that suggests Levothyroxine is used in this way. The science of doping is frighteningly advanced
Stress fractures sound nasty but can be better than tendon trouble. 4 to 6 weeks done! Then re-build your training slowly, take some calcium tablets you will be fine! Generally the more rest the quicker the healing process.
It is worth knowing that stress fractures can give you pseudo pain even after the bones have healed. This makes restarting training difficult to judge, a physio could help with this.
Thanks SideBurn. The pain is dull rather than sharp so it looks more like a stress fracture than tendonitis.
Your GP should be able to confirm yes or no; either way the remedy is rest. Stress fracture is 4 to 6 weeks but when healed they are healed. Tendonitis can hang around. Good luck! But experiment with different lacing styles
Try feeling down the bones on the top of your foot (metatarsals), can you feel any swelling on the bone or pain when pushing on the bones? Is the pain dull? These would indicate a stress fracture rest and calcium tablets.
If the pain is sharp and more general then tendonitis; again rest and ibuprofen (if you can take it) try re-lacing your shoes so that you miss the crossovers that are over the injury. Just go in and out through the loops so there is no pressure on the affected area.