PHY3181 Lecture Notes - Lecture 7: Leydig Cell, Night Sweats, Twin Study
30 Jun 2018
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Lecture 11: Puberty and aging
Puberty is the transformation from a child to
an adult – the transition from sexual
immaturity to fertility during which secondary
sexual characteristics develop (the process
through which a child matures and becomes
capable or reproduction).
Reproduction is possible once full activation of
reproductive signalling is achieved.
• In female: first period (menses/
menarche)
• In male: first ejaculation (spermarchy/
seminarchy)
Puberty involves:
• Progressive activation of the HPG axis
• Progressive development of secondary
sexual characteristics under the
influence of endocrine signalling
Note that we do not know what initiated
puberty.
Stages of puberty/ hallmarks of physical
changes
Adrenarche: normal pre-pubertal increase in
adrenal androgen production prior to onset of
physical signs of puberty.
Pubarche: appearance of pubic hair
Gonadarche: activation of HPG axis signalling,
associated with the pubertal growth – period
of rapid height gains (second largest growth
spurt following neonatal growth – growth
hormone drives this growth spurt)
Thelarche: appearance of breast tissue (no
male counterpart)
Menarche: onset of the first menstrual period
(menses)
Spermache/ seminarche: development of
mature sperm in male ejaculate
Two in red = very involved with the underlying
pubertal changes occurring
Tanner stages of puberty
• 1 is pre-pubertal or infertile stage
• 2-4 are intermediate stages of
development
• 5 is complete adult development
Note that the physiological changes are
continuous – we classify them in stages
Male tanner stages
Tanner I. is prepubertal; testicular volume
<1.5ml, small penis 3cm or less (<9years)
Tanner II. Testicular enlargement (1.5-6ml),
skin on scrotum thins, reddens and enlarges,
penis length unchanged (9-11years)
Tanner III. Testicular volume between 6 and 12
ml; penis begins to lengthen to 6cm. (11-
12.5years)
Tanner IV. Testicular volume between 12 to 20
ml; scrotum enlarges further and darkens,
penis increases to 10cm (12.5-14years)
Tanner V. testicular volume greater than 20ml;
adult scrotum and penis of 15cm in length
(14+years)
Note that throughout puberty the changes in
testicular volume are the most significant. An
orchidometer is a medical instrument used to
measure testicular volume. First signs of
puberty testicular volume of 4mls.
Testicular changes in puberty
There is a change in composition –
predominantly in the germ cells these
proliferate with onset of spermatogenesis
Tanner stages in females
Tanner I. pre-pubertal; no glandular tissue,
areola follows the skin contour of the chest
(<10years)
Tanner II. Breast buds form, with small area of
surrounding glandular tissue; areola begins to
widen (10-11.5)
Tanner III. Breasts become more elevated, and
extend beyond the borders of the areola,
which continues to widen but remains in
contour with breast (11.5-13 years)
Tanner IV. Increased breast size and elevation;
areola and papilla form a secondary mound
projecting from the contour of the breast (13-
15 years)
Tanner V. breast reaches final adult size;
areola returns to contour of the surrounding
breast with a projecting central papilla (15
years)
Note than women experience puberty earlier
than males (around 2 years). There are very
broad ranges in the onset of stages (lots of
individual variation)
Factors known to affect the onset of puberty
• Genetics (from twin studies) – explains
50-80% of variation of onset
• Ethnicity (pubertal onset is earlier in
African American and Hispanic
Document Summary
Note that the physiological changes are continuous we classify them in stages. Reproduction is possible once full activation of reproductive signalling is achieved. Puberty involves: progressive activation of the hpg axis, progressive development of secondary the sexual characteristics under influence of endocrine signalling. Note that we do not know what initiated puberty. Adrenarche: normal pre-pubertal increase in adrenal androgen production prior to onset of physical signs of puberty. Gonadarche: activation of hpg axis signalling, associated with the pubertal growth period of rapid height gains (second largest growth spurt following neonatal growth growth hormone drives this growth spurt) Thelarche: appearance of breast tissue (no male counterpart) Menarche: onset of the first menstrual period (menses) Spermache/ seminarche: development of mature sperm in male ejaculate. Two in red = very involved with the underlying pubertal changes occurring. Testicular enlargement (1. 5-6ml), skin on scrotum thins, reddens and enlarges, penis length unchanged (9-11years)
