calcitonin in blood

1.-What is the problem, if a child has low concentration of calcitonin in blood? ?

2.-Where are produced the ADH and oxytocin?

3.- Please explain all the steps of the Renin-Angiotensin-Aldosterone axis.

4.- Why the heart and the thymus are considered organs with secondary endocrine functions? Please explain.

5.- Please explain Follicular phase and Luteal phase.

no copy and paste