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Physical Growth and Development during Adolescence

Annie Hoopes Adolescent Medicine Fellow/LEAH Senior Fellow November 8, 2013

Overview

•  Context •  Features of puberty •  Evaluation of pubertal

development •  Adolescent brain

development •  Resources

Features of Puberty

Puberty Basics

•  Outcomes of puberty •  Adult size and appearance •  Clear distinction between sexes •  Ability to reproduce

•  Physical changes reflect hormonal changes •  Onset

•  Girls: Age 7 to 13 years •  Boys: 9 to 14 years

•  Rate •  5 years for girls •  6 years for boys •  Differences in timing and rate by gender/ethnicity

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Definitions

•  Adrenarche – adrenal cortex starts producing androgens

•  Gonadarche – gonads activated by follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

•  Pubarche – appearance of pubic hair •  Thelarche – appearance of breast tissue •  Menarche – age of onset of first menstrual period •  Spermarche – age at first ejaculation

Hormones of puberty

•  Hypothalamic-pituitary-gonadal axis •  Adrenal system

Hypothalamic-Pituitary-Gonadal (HPG) Axis HPG Axis: After Puberty

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LH and FSH

LH FSH

MALES Testosterone production from Leydig cells

Sperm production from Sertoli cells

FEMALES

Androgen production from theca cells Progesterone production from the corpus luteum Mid-cycle surge ! ovulation

Ovarian follicle development Estrogen production from granulosa cells

Testosterone and Estrogen

Testosterone Estrogen

MALES

Growth of penis and scrotum Growth of pubic/facial hair Deepening of voice Increased libido Increased muscle mass Acne Thickening of cortical bone

**Peripheral conversion Low levels: pubertal growth spurt, accrual of peak bone mass High levels: closure of epiphyses

FEMALES Thickening of cortical bone Growth of pubic hair

Bone effects as in males Growth of breasts, labia, vagina, uterus Pattern of fat deposition Vaginal pH " and length # Proliferation of endometrium Triggers LH surge

Onset of Puberty

•  Trigger for puberty not completely understood •  50-80% of variation in onset likely genetics •  Change in body composition = permissive role •  Threshold % of body fat is likely necessary but

not sufficient for onset (↓Leptin ⟶ ↓ LH pulse ⟶ pubertal suppresion)

•  Other factors •  Inhibitory central feedback mediated by

neurotransmitters (GABA, neuropeptide Y) •  Gonadotropin releasing

hormone pulse generator becomes increasingly active – first nocturnally then during the day

Adrenal System

Occurs peripherally (outside of the adrenal gland)

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How do we measure puberty?

•  Timing is variable but SEQUENCE is predictable

•  Chronologic age correlates poorly with biological maturity

•  Assess maturity with Sexual Maturity Rating (Tanner) scale or skeletal age/bone age

SMR (Tanner) Stages - Males

1: Prepubescent, no pubic hair 2: Enlargement of testes >2.5cm or 4 cc volume, reddening of scrotum, no change in penis (**1.5 years before growth spurt), sparse pubic hair 3: Penis and scrotum grow, pubic hair darker and coarser 4. Scrotal darkening, penis grows in width (fertility, voice changes), hair extends up 5. Adult size penis and testes, hair extends to thighs

SMR (Tanner) Stages - Males SMR (Tanner) Stages - Females

1: Prepubescent, no breast tissue 2. Breast buds, sparse pubic hair) 3: Enlargement of breast, no separation of areola from breast, pubic hair coarser and darker 4. Areola and papilla project above breast, forming secondary mound, pubic hair extends up 5. Areola recedes to match contour of breast, papilla projects beyond areola, pubic hair extends to thighs

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SMR (Tanner) Stages - Females Peak height velocity

Timing of pubertal events Body Composition

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Timing of pubertal events

Males

Females

What’s too early? Or too late?

Girls Breast Changes: •  Early<7-8 in girls •  Late>13 in girls Pubic Hair: •  Early<7-8 in girls •  Late>13 in girls Menarche: •  Too late>15-6 (or > 5 yrs

from TS-II breasts)

Boys Gonad changes: •  Early <9 in boys •  Late >14 in boys Pubic Hair: •  Early <9 in boys •  Late >15 in boys Duration of Puberty: •  Too long>5 yrs from TS

II-V

Puberty – Getting Earlier?

Menarche: •  1850s!1950s - mean age of menarche ↓

from 17 yrs! 12.5 yrs in U.S./Western Europe

•  Timing of menarche relatively stable since 1960s in U.S.

Breast Development: •  ? ↓ since the 1970s in the United States:

1970s : age 8 1997 : age 7 (white girls) and age 6 (African American girls)

! ? Due to changes in nutritional, health, & SES, other causes (?endocrine disruptors?)

Case #1

•  A 14yo male comes into your office. You detect upon walking into the room that he needs to start wearing deodorant. You also note that he has some mild facial acne and some axillary hair.

(1) Should you conclude that he is going through puberty normally?

(2) Which system causes these changes?

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Case #1

•  A 14yo male comes into your office. You detect upon walking into the room that he needs to start wearing deodorant. You also note that he has some mild facial acne and some axillary hair.

(1) Should you conclude that he is going through puberty normally? •  Not necessarily.

(2) Which system causes these changes? •  These are all signs that his ADRENAL SYSTEM is producing

hormones, but does not tell you anything about the H-P-G axis.

Acne

•  Can be part of normal development

•  Can contribute to negative self-image

•  Caused by the adrenal system

•  If severe acne and other signs/symptoms of androgen excess •  Consider endocrine disorder

(eg non-classic congenital adrenal hyperplasia)

Case #2

•  A 12 yo male presents with pain and swelling in his right nipple

(1) What do you want to know? (2) What can you tell him about this condition?

Case #2

•  A 12 yo male presents with pain and swelling in his right nipple

(1) What do you want to know? •  Is puberty progressing

normally? •  Is he on any medications?

Taking any drugs? •  Does he have any chronic

illnesses?

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Gynecomastia

•  Glandular development due to changes in hormone levels during puberty (estrogenic-androgenic balance)

•  1/3 of healthy guys •  Usually resolves in 3-24 mos without intervention •  Assessment/management

•  Careful history for common drug culprits (drugs of abuse, antipsychotics, reflux meds, antifungals) or chronic disease

•  Physical exam to assess for true vs. pseudogynecomastia •  Monitor every 3-6 mos until resolved •  Consider treatment or surgical referral is lasting longer than 12

mos, causing discomfort/embarrassment, and adult testicular size has been attained

Case #3

•  An 11 year old female comes into your office for a sports physical. Name 2 common musculoskeletal complaints that occur in adolescence and are impacted by skeletal maturity.

Hints! Answers

•  Osgood Schlatter: •  Caused by overuse!chronic avulsion of tibial tubercle growth

plate •  Usually happens in athletic adolescents right after growth spurt

(i.e., age 13-14 in boys, age 11-12 in girls) •  Clinical diagnosis: appropriate history, tibial tubercle swelling

•  Scoliosis: •  80-85% adolescent onset •  Progression more common in girls once diagnosed •  Once skeletal maturity occurs, will not progress •  Indications for referral to an orthopedic surgeon

•  Angle of trunk rotation (as measured with the scoliometer) of ≥7º, Cobb angle ≥20º, and progression of Cobb angle of >5º

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Other common issues

•  Anemia (9% of adolescent girls = iron deficient) •  Myopia (caused by growth in axial diameter of the eye) •  Dysfunctional uterine bleeding (80% due to anovulation) •  STIs (peak incidence of many STIs 15-24 years) Adolescent Brain

Development

Adapted with permission from Doug Diekema, 2013

Adolescent Brain Development

Adapted with permission from Doug Diekema, 2013

Previous knowledge of adolescent brain

•  Adolescents often do not perform at a level commensurate with their cognitive abilities

•  Middle adolescents are more likely than younger adolescents to rely on analytic processing, but this is not their primary means of decision making

•  Middle and older adolescents have the ability to make adult-level decisions (ie possess competence) but frequently do not use that ability or maximize use of those abilities

Klucyznski. Child Development 2001; 72:844

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New Science of the Teenage Brain

Adapted with permission from Doug Diekema, 2013

“Two” Brain Systems

•  Balance between the two systems: •  “Rational” : pre-frontal cortex •  “Emotional” : Limbic structures, ventral striatum

•  Both have value, either can mislead •  “Emotional” systems most adaptive for humans living in

small communities (responds to individuals, crisis, reward – less utilitarian)

Epstein. Stanford Social Innovation Review. Spring 2006.

Adapted with permission from Doug Diekema, 2013

Scarecrow and Tin Man

Adapted with permission from Doug Diekema, 2013

“Emotional” Brain

•  Picks up patterns before consciously aware of them •  Motivates behaviors change through feelings, autonomic

repsonses •  First impressions •  Often based on a “thin-slice” of available information

Gladwell. Blink. NY: Little, Brown, & Co, 2005.

Adapted with permission from Doug Diekema, 2013

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What does the prefrontal cortex do?

•  High level reasoning •  Decision-making •  Impulse control •  Assessment of consequences •  Planning, strategizing, organizing $•  Inhibit inappropriate behavior •  Adjust behavior when

situation changes •  Setting priorities •  Estimating and understanding probabilities

Adapted with permission from Doug Diekema, 2013

Adolescent Brain Development

•  Extensive Remodeling and Pruning •  Increased Linkages

•  Corpus Callosum thickens •  Stronger links between Hippocampus

(memory) and Frontal areas (goals and agendas)

•  Increased Myelinization

Adapted with permission from Doug Diekema, 2013

Impact of Changes

•  Improved balancing of impulses, desires, goals, self-interest, rules, ethics, etc.

•  Integration of memory and experience into decision-making

•  Improved planning •  Improved balance in considering immediate rewards and

future consequences

Adapted with permission from Doug Diekema, 2013

Adolescent Brain Development

•  Not fully matured till mid 20s •  Maturation occurs “back to front” $•  Pre-frontal cortex is last to mature •  Imbalance: Less active pre-frontal, more active

reward response system (ventral striatum) and limbic system

•  Males vs. Females

Adapted with permission from Doug Diekema, 2013

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Prefrontal Cortex vs. Limbic System

•  PFC: •  Situation % assess % plan $•  (STOP) of survival

•  Limbic System: •  Situation % emotion/feeling % react

Adapted with permission from Doug Diekema, 2013

“The adolescent brain has a well-developed accelerator but only a partially developed brake” --Laurence Steinberg

Adapted with permission from Doug Diekema, 2013

Why?

•  Once myelinization is complete and connections are established, learning slows down and the brain becomes less nimble and adaptable.

•  If the brain completed development earlier, the period of learning would be lost.

•  “If we smartened up sooner, we’d end up dumber” (David Dobbs in National Geographic, October 2011)

Adapted with permission from Doug Diekema, 2013

Why?

•  Evolutionary perspective •  Adolescent: Movement from safety of home to

complex outside world •  Requires adaptability, willingness to take risk •  Sensation seeking: enhances learning, social

connections •  Risk-taking: The young warrior

Adapted with permission from Doug Diekema, 2013

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Implications: PFCDD?

•  Impulsive, inflexible •  Aggressive, Reckless •  Emotionally volatile •  Risk-taking: less sensitive to risks and more sensitive to

possible rewards •  Reactive to stress •  Vulnerable to peer pressure •  Respond to short term- rewards, excitement, arousal •  Underestimate long-term consequences •  Overlook alternatives

Adapted with permission from Doug Diekema, 2013

The Adolescent Brain: Summary

•  Imbalance between development of pre-frontal (later) and sub-cortical areas (early)

•  Very sensitive to environmental cues, affective elements, rewards and punishments

•  Thrill seeking and risk taking. Impulsive •  Brain is very good at decision-making tasks •  Brain is not very good at making decisions in emotionally

charged situations •  Decisions may weigh current rewards and feelings at

expense of future implications

Adapted with permission from Doug Diekema, 2013

Implications

•  Adolescents are capable of making rational decisions •  Less likely to be able to do so under conditions of high

emotion or intense pressure (including peer pressure) •  More likely to act impulsively without full consideration of

consequences •  Psychosocial and emotional contributors interact with

cognitive aspects of decision-making •  Emotional or “Gut Response” vs. Reason

Adapted with permission from Doug Diekema, 2013

Putting it all into context

NCHS Data Brief ■ No. 37 ■ May 2010

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Putting it all into context Resources •  http://www.greatconversations.com •  www.scarleteen.com •  http://www.pbs.org/wgbh/pages/

frontline/shows/teenbrain/

No. 95 December 2011 The Teen Brain: Behavior, Problem Solving, and Decision Making Many parents do not understand why their teenagers occasionally behave in an impulsive, irrational, or dangerous way. At times, it seems like they don’t think things through or fully consider the consequences of their actions. Adolescents differ from adults in the way they behave, solve problems, and make decisions. There is a biological explanation for this difference. Studies have shown that brains continue to mature and develop throughout childhood and adolescence and well into early adulthood.

Scientists have identified a specific region of the brain called the amygdala which is responsible for instinctual reactions including fear and aggressive behavior. This region develops early. However, the frontal cortex, the area of the brain that controls reasoning and helps us think before we act, develops later. This part of the brain is still changing and maturing well into adulthood.

Other specific changes in the brain during adolescence include a rapid increase in the connections between the brain cells and pruning (refinement) of brain pathways. Nerve cells develop myelin, an insulating layer which helps cells communicate. All these changes are essential for the development of coordinated thought, action, and behavior.

Changing Brains Mean that Adolescents Act Differently From Adults

Pictures of the brain in action show that adolescents’ brains function differently than adults when decision-making and problem solving. Their actions are guided more by the amygdala and less by the frontal cortex. Research has also demonstrated that exposure to drugs and alcohol before birth, head trauma, or other types of brain injury can interfere with normal brain development during adolescence.

Based on the stage of their brain development, adolescents are more likely to:

x act on impulse x misread or misinterpret social cues and emotions x get into accidents of all kinds x get involved in fights x engage in dangerous or risky behavior

Adolescents are less likely to:

x think before they act