What are the causes of hyperthyroidism?

It can be from any injury to the thyroid. It is usually an autoimmune condition where the body's immune system, which usually fights infections, attacks the thyroid gland.

Yes, although generally not permanent infertility

When the thyroid is overactive it releases more thyroxin. Thyroxin, in a nutshell, tells your body how fast to go. If you have too much thyroxin stimulating your heart then it will beat faster. The...

Yes, I have this disorder and I hate eating breakfast but not eating enough nutrients accelerates the fatigue and weakness and these triggers diziness.

No. But it can coexist with a swelling of the thyroid which may superficially look a bit like lymphadenopathy.