Embryonic Development and Why Men Have Nipples

• Both men and women have nipples due to embryonic formation timing
• SRY Y gene (sex determining region Y) on Y chromosome activates at 7 weeks
  • Leads to male reproductive organ development
  • Female reproductive organs disappear
• Breasts and nipples form before SRY gene activation
• All humans have nipples and mammary ridge regardless of sex

Male Lactation

• Male nipples can lactate - rare but documented
• Men typically don't produce enough prolactin (hormone stimulating milk production)
• Prolactin level surges in men can result from:
  • Hypothyroidism (impacts pituitary gland)
  • Medications: anticholinergics, chlorpromazine, steroids, heart medication digoxin
  • Estrogen or prolactin supplementation
• One study showed male breast milk had same concentrations of lactose, proteins, electrolytes as women's colostrum/milk
• Dr. Shani Dour (Stanford University): no evidence suggesting difference between cisgender women and other breastfeeding parents' colostrum

Nipple Sensitivity and Sexual Function

• Nipple stimulation activates same brain areas as genital stimulation
• Journal of Sexual Medicine study used MRI to map brain activation
• Genital sensing brain areas in women correspond to same areas in men
• Rutgers University psychologist Barry Komisaruk: "nipple finding was surprise"
• Speculation: basis for nipple stimulation being erogenous

Exercise-Related Nipple Issues

• Nipples can chafe and bleed during physical activity
• Common in marathon runners - red streaks down chest
• Caused by friction from skin rubbing against clothing
• Prevention methods:
  • Remove shirt or pull away from nipples
  • Apply hydrogen peroxide after race (stings but helps)
  • Use antibiotic ointment and bandages
  • Invest in nipple guards (better than regular bandages)
  • Avoid cotton, wear synthetic/moisture-wicking fabrics
  • Stay hydrated - reduces chafing risk by preventing salt crystal formation

Third Nipples (Supernumerary Nipples)

• 1% of men have third nipple
• Also called polymastia or polythelia
• ~200,000 Americans have one or more extra nipples
• Possible to have up to 8 nipples
• More common in men than women
• Usually appear along "milk line" (armpit through nipples to genitals)
• Outside milk line = ectopic supernumerary nipple
• Six categories:
  1. Nipple with areola and breast tissue underneath
  2. Nipple with breast tissue, no areola
  3. Breast tissue without nipple
  4. Breast tissue without areola or nipple
  5. Pseudo mama - areola with fat tissue instead of breast tissue
  6. Polythelia - nipple alone, no areola or breast tissue
• Formation: during 4th week pregnancy, milk lines thicken
• If ectoderm tissue doesn't soften properly, supernumerary nipples form
• Mostly harmless, can be removed for cosmetic reasons
• Can lactate like regular nipples

Cultural Attitudes and Censorship

• Media censors female nipples but allows male nipples
• Japan 2015: men removing undershirts in heat caused controversy
• Goo search engine survey: "see-through nipples" (sukichikubi) was most hated male fashion trend
• Some women considered it sexual harassment
• Japan has summertime nipple concealer industry for men
• Historical context (Michael Bronsky, Harvard): male nudes represented virtues like patriotism, strength; female nudes more sexualized

Male Breast Cancer

• At least 2,400 men diagnosed annually
• Usually in older men but can occur at any age
• Everyone born with some breast tissue = anyone can get breast cancer
• Treatment: surgery to remove breast tissue, chemotherapy, radiation therapy
• Symptoms:
  • Painless lump or skin thickening on chest
  • Skin changes: dimpling, puckering, scaling, color changes
  • Nipple structure changes, inward turning
  • Discharge or bleeding from nipple
• Cancer types in men:
  • Ductal carcinoma (most common) - begins in milk ducts
  • Lobular carcinoma - begins in milk-producing glands (less common in men)
  • Paget's disease of nipple - rare, affects males over 50
  • Inflammatory breast cancer
• Paget's disease symptoms: flaky/scaly skin, crusty/rusty oozing, itching, redness, tingling, discharge, flattened/inverted nipple

Gynecomastia

• Increase in breast gland tissue in males
• Caused by estrogen/testosterone imbalance
• Can affect one or both breasts
• Occurs in newborns, during puberty, or older age
• Can cause pain, embarrassment, self-consciousness
• May resolve on its own or require medication/surgery
• Results in puffy or pointy nipples
• Unrelated to chest muscle - doesn't improve with weight loss/exercise

World Records and Unusual Facts

• The Baron (Finland): heaviest weight lifted by nipples - 71.87 lb (32.6 kg), July 19, 2013, Bush Hall, London
• Sage Weach (Great Nippulini): heaviest vehicle pushed by nipples - 21,792 lb (9,885 kg) vehicle for 65.62 ft (20 M), March 25, 2011, Milan, Italy
• Daniel Tui (Italy): longest nipple hair - 6.69 in (17 cm), March 2013
• Age restriction for records: 16+ years old

Montgomery Glands

• Named after William Featherstone Montgomery (1837)
• Small sebaceous glands in nipple and areola
• Secrete oily/waxy substance for lubrication
• Prevent sore/cracked nipples during breastfeeding
• Protect babies from germs, guide babies to latch through scent
• Both men and women have them (formed before sexual dimorphism)

Unusual Injuries

• Leonard Overcash (Mogi, Oklahoma, 2015): zebra bit off part of his nipple
• Zebra owned illegally for 10 years, owner claimed ignorance of permit requirements
• Owner paid medical bills, given 30 days to rehome zebra
• Overcash described ordeal as painful and traumatizing but recovered quickly