I was diagnosed less than a year ago as having, secondary hyperparathyroidism. Sounds serious doesn't it, but it is quite simply put in plain English as Calcium shortage. This is controlled by taking a calcium tablet each day, and getting my blood checked regularly, to ensure I am taking enough calcium. Calcium shortage sounds innocuous, until you look up why your body needs calcium, and the things a shortage can cause. I don't like having to take so much medication...and the calcium tablets are huge....nope...you don't swallow them, they are suck or chew ones.
Anyway tiredness is a symptom and towards the end of a day I start flagging.