Not an adequate response from the GP, IMO. They should be checking whether is is precocious puberty, or premature adrenarche, as true precocious puberty might need treatment.
OP, my dd had the following tests done:
- Ultrasound scan of womb and kidneys to check for tumours on adrenal glands or advanced development of womb
- Blood test (poor dd) to check hormone levels
She has premature adrenarche and will be seen by the consultant 2-3 times a year until she reaches age 8 or so, when puberty can be classed on the young side of normal. I've been told to tell them immediately if she starts to show any signs of bleeding or breast development - the other symptoms, such as pubic hair, underarm hair or increased body odour, are increased sensitivity to the sex hormones (sorry, I'm paraphrasing the consultant), but not indicators of true puberty.
It's a shock, but do push for a referral, for your peace of mind.