A 16 year old girl moderately built and nourished came with history of delayed cycles and weight gain of 3-5 kgs in a month. On examination nothing significant detected. All parameters like hemogram, thyroid profile including Free T 3, T 4 and TSH, rft, lft, rbs, hba1c, c-peptide, harmonal assay, crp, esr we're within normal limits. Abdomino-pelvic u/s scan reveals slightly larger follicles, otherwise within normal limits.

No significant past or family history. What's the cause of delayed cycles and weight gain? What's the management plan?