Secondary amenorrhoea and oligomenorrhoea

1. Big picture

Secondary amenorrhoea and oligomenorrhoea are disorders of menstrual frequency. In the oral exam, the examiner wants to hear one safe, logical sentence first:

Always rule out pregnancy first, then localize the problem along the hypothalamic–pituitary–ovarian–endometrial–outflow tract axis.

The key clinical idea is simple:

Hypothalamus → GnRH pulses
        ↓
Pituitary → FSH + LH
        ↓
Ovary → follicle growth + ovulation + oestrogen/progesterone
        ↓
Endometrium → proliferation + secretory transformation
        ↓
Outflow tract → visible menstruation

Amenorrhoea occurs if any step fails: **no hormonal signal, no ovarian response, no en