MALE REPRODUCTIVE PHYSIOLOGY II

Dr. Nilesh Kate(MBBS. MD)

DR NILESH N KATEASSOCIATE PROFESSORESIC MEDICAL COLLEGE

GULBARGA.

ENDOCRINAL FUNCTIONS OF

TESTES

MALE REPRODUCTIVE PHYSIOLOGY

Depends On Testosterone Testicular Leydig Cells Secrete Testosterone Sertoli Cells Secrets Inhibin, Oestrogen, And

Activin. Testes Descend And Pass Out Of Abdominal

Cavity

TESTOSTERONE Leydig cells -- interstitial connective tissue

between seminiferous tubules. Numerous in Newborn and after puberty Childhood scanty Decreases after 40 and absent in old age i.e.

around 80 years of age. Normal secretion 4-9 mg /day Plasma testosterone 0.65 microgram %

DERIVATIVES OF TESTOSTERONE

Insert fig. 20.14

TRANSPORT IN PLASMA 2 % in free form 98 % in bound to plasma proteins form 68 % --- albumin. 30% --- testosterone binding globulin i.e. sex

steroid binding globulin . (SSBG)

ANDROSTENEDIONE Steroid precursor for blood Oestrogen 2.5 mg/day

DIHYDROTESTOSTERONE

■ Testosterone converted into

Dihydro testosterone by 5 ά reductase.

■ Has more than twice biological activity.

FORMATRION OF ANDROGEN

CHOLESTEROL

PRGNENOLONE

PROGESTERONE

ANDROSENEDIONE

TESTOSTERONE

DIHYDROTESTOSTERONE DIHYDROTESTOSTERONE

17ά HYDROXY-PREGNENOLONE

DEHYDROXYEPIANDROSYTERONE

ANDROSENEDIONE

KEY STEP

IN TESTES

FUNCTIONS OF TESTOSTERONE

Before birthAt puberty In adults

TESTOSTERONE: BEFORE BIRTH

Effect on sex differentation in fetusGonadal sex differentation

Y chromosomes – TDF MIS

Genital differentation internal genitaliaExternal genitalia

Effect on descent of testes from abdomen to testisCryptorchidism

Gonadal Differentiation1. Genital Ridge

2. Bipotential Gonads

BIPOTENTIAL GONADS

testes ovaries

TDF NO TDF

TESTOSTERONE NO TESTOMISNO MIS

Degenerates MULLERIAN (Parameso) uterus and tubes

epididymis, vas def.& ejaculatory ducts form WOLFFIAN (Meso) degenerates

Genital differentiation

PUBERTY IN THE MALE Usually 10-14 years old Endocrine, physical, and behavioral growth. Leydig cells “awake”

TESTOSTERONE: AT PUBERTY

■ EFFECTS ON EXTERNAL GENITALIATESTOSTERONE – Enlargement of penisDHT – Scrotum size , pigmentation, Rugal folds

■ EFFECT ON ACCESSORY SEX ORGANSTESTOSTERONE -- SEMINAL VESICLESDHT -- PROSTATE SIZE AND SECREATIONS■ MALE SECONDARY SEX CHARACTERBody hair – male pattern, beard growthVoice – Due To Larynx Enlargement, Low PitchMuscle mass and shoulder girdleChanges in skin – thicker & darker.

EFFECT ON PSYCHEPshychological differtiationLibido – initiate sexual driveAggressive behaviour

ANABOLIC AND GENERAL GROWTH PROMOTING EFFECT.Nitrogen retention - misuse Bone growth – Somatomedins C levelBasal metabolic rate Water electrolyte balance

TESTOSTERONE: IN ADULTS

Hair Growth – Male baldness. Psyche – behavioral attitude Bone – prevent bone loss & osteoporosis. Spermatogenesis Haematopoiesis Circulating and stored body fats :-

LDL HDL Gonadotrophins secretion Suppression of

LHRH, LH.

Direct Gene Activation

Receptor/hormone Complex

mRNA

Protein

Aldosterone Cortisol Testosterone Estrogen Progesterone Thyroxine

MODE OF ACTION OF ANDROGENS

CONTROL OF LH AND FSH SECRETION Negative feedback:

Testosterone inhibits LH and GnRH production.

Maintain relatively constant secretion of LH and FSH.

Declines gradually in men over 50 years of age.

Testosterone converted to DHT, which inhibits LH.

Inhibin inhibits FSH secretion.

Aromatization reaction producing estradiol in the brain, is required for the negative feedback effects.

Insert fig. 20.13

ENDOCRINE FUNCTION OF THE TESTES

■ Testosterone and its derivatives are responsible for initiation and maintenance of body changes in puberty.■ Stimulate growth of

muscles, larynx, and bone growth until sealing of the epiphyseal discs.

Promote hemoglobin synthesis.

Act in paracrine fashion, responsible for spermatogenesis.

Insert fig. 20.15

Hormonal Control of Spermatogenesis Formation of primary spermatocytes and entry

into early prophase I, begin during embryonic development. Spermatogenesis arrested until

puberty. Testosterone required for completion of meiosis

and spermatid maturation. Secrete paracrine regulators:

IGF-1. Inhibin. Transforming growth factor.

FSH necessary in the later stages of spermatid maturation.

ESTROGEN SECRETION

Sertoli and Leydig cells secrete small amounts of estradiol. Receptors found in Sertoli and Leydig cells and

accessory organs. May be responsible for:

Negative feedback in brain. Sealing of epiphyseal plates. Regulatory function in fertility.

APPLIED ASPECTS

CryptorchidismExtirpationHopogonadism in malesHopergonadism in malesMale infertilityVasectomy

CRYPTORCHIDISM (Gk. kryptos – hidden + orchis - testis)

■ In 97% of male newborns, testes are present in the scrotum before birth.■ In most of the remainder, descent will be completed during the first 3 months Postnatally.■ However, in less than 1% of infants, one or both testes fail to descend.

CRYPTORCHIDISM The condition is called

Cryptorchidism and may be caused by decreased androgen (testosterone) production.

The undescended testes fail to produce mature spermatozoa and the condition is associated with a 3% to 5% incidence of renal anomalies.

EXTIRPATION Removal of testes. Before puberty --- ENUCHOIDISM CHARACTERISED BY

Permanent sterilityUnderdevelopment of external genitaliaUnderdevelopment of secondary sex character.Abnormal bone growth.

HOPOGONADISM IN MALES

Absent or deficient testicular hormone. Due to –

congenital non functioning of testes.Absent HCG.CryptorchidismExtirpation of testes.Absent androgen receptors

■ Frohlich’s syndromeObesity along with Enuchoidism

HYPERGONADISM IN MALES

Excessive secretion in tumors of Leydig cells.

Precocious pseudo pubertyRapid growth of muscles

and boneSex organs and secondary

sex characters at early age.Also secretes Oestrogen so

develops Gynecomastia.

INFERTILITY Inability of sperm to fertilize ovum Due to

-- Androgen dysfunction with normal sperm count.

-- Isolated dysfunction of sperm cell production-- Combined androgen and sperm cell production defects.-- Failure of deposition of sperm in female genital tract.

VASECTOMY Permanent method for sterilization in males Vas deferens

cut and ligated

THANK YOU

Sunday, April 26, 2015