Introduction

Puberty is the physiological sequence of events when secondary sexual characteristics develop and reproductive capacity is achieved. The start of puberty is characterised by the appearance of a palpable breast bud (stage B2) in girls and testicular volumes of >3.5 ml in boys. These changes are brought about in response to the pulsatile secretion of gonadotropin releasing hormone (GnRH) from the hypothalamus stimulating the release of follicle stimulating hormone (FSH) and luteinising hormone (LH) from the anterior pituitary. It is still unclear why the GnRH neurons are usually inhibited after infancy until the start of puberty, although fat mass (via leptin signalling) and kisspeptin secreting neurons stimulating the GnRH system certainly play a role. LH acts on the gonads to increase the secretion of oestrogen in the female or nocturnal testosterone in the male that then promote growth in target tissues. FSH acts on the gonads to produce ovum or sperm, respectively. Androgens in particular promote other secondary sexual characteristics such as smelly feet and axillae, acne, body odour and mood swings – often most noticeable to the parents.

The timing of puberty is very variable and is dependent on socioeconomic status, ethnicity, nutritional and genetic factors. There has been an apparent secular trend in the onset of female puberty, although the mean age of menarche has remained fairly stable during the last 2 decades, implying that the duration of puberty may be increasing in girls.1 Hence, the definition of early or late puberty is fairly arbitrary. In the UK, the ranges for normal onset of puberty are shown on the growth charts,2 with the 98th centile for start of testicular enlargement just less than 9 years in a boy and just over 8 years for B2 in a girl. Similarly, only 2% of boys have not started …