Thyroid problems in general can cause irregular periods with abnormal flow patterns as well. This includes both hyperthyroidism and hypothyroidism.
Frequent spotting that is out of your usual menstural cycle is also known as intermenstural bleeding.
There can be many other causes for this such as infections, hormonal imbalances, polyps etc.
Hence the best advice would be for you to see a doctor for further evaluation to ascertain the exact cause for your symptoms if you are experiencing frequent spotting.
Regards,
Dr Michelle Chia