“What cause the heart to skip a beat?”

First of all, you need to see a cardiologist to set up a heart monitor. There are many different types of arrhythmias that can result in the sensation of "skipped beats" and it is important to see what they. Fortunately, most of them are benign and have multiple potential minor causes ranging from stress, dehydration, alcohol, caffeine to gastric reflux among many other things. Yet a small percentage are from more serious causes that can be tested for after the type of rhythm abnormality is known.

Hi!

Skipped beats are caused by many reasons based on patient condition and age. In your case, it is probably benign condition called PVCs or PACs. However, caffeine, anxiety, alcohol - all can make thyroid conditions worse. And rarely, it is an indication for underlying heart disease. So, you can start to avoid that and see how it goes.
Hope it helps.