In case the islets of Langerhans stop functioning which hormone will be in short supply and what will be its effect

In case of stoppage of functioning of islets of Langerhans which hormone will be in short supply & what will be its effect?

What will happen if Islets of langerhans fall to function ?

Which cells of islet of Langerhans secrete insuliun ?

Which hormone is secreted from the testes and what is its function?

Which hormone is secreted by Pineal gland? What is its function?

How does the short circuit form? What is its effect?

Location/Function : Islets of Langerhans