HYPOTHALAMO-PITUITARY-OVARIAN AXIS Roots to Obstetrics & Gynaecology Prof. Hemantha Dodampahala (MBBS, MD, FRCSE, FRCOG. FISUOG) Dept of Obstetrics & Gynaecology Faculty of Medicine, Colombo
Physiology Hypothalamo- Pituitary - Ovarian Axis (HPOA) GnRHH FSH / LH P OestrogenO Negative feedback Maintains homeostasis
Spectrum of events in both sexes Birth Puberty Menarche /adrenarche Reproduction / coitarche Climacteric Menopause /Andropause
Genotype and Phenotype Genetic sex determines the gonad based on Y chromosome (SRY) Testosterone/DHT Anti-Müllerian Hormone LH FSH via GnRH (HPO axis) fetal, early infancy, childhood, late pre-puberty and puberty
Puberty Altered endocrine system occurs years earlier to physical, mental and social change Fetal – GnRh neurone activity at 12 week Male – T secreted from 7 weeks and peaks weeks Female – maintenance of oöcyte population depends on normal X chromosome complement
Puberty, Menarche and Primary Amenorrhoea Breast Development Pubic hair growth Axillary hair growth Growth – Increase in body contours, proteins, fat = weight gain Menarche ** Good practice is to check the items in order in case of primary amenorrhoea Mean age of puberty Menarche before 16 years
HYPOTHALAMUS GnRH Pituitary FSH / LH Gonad ESTROGEN/TESTOSTERONE Negative feedback Positive feedback for LH ovulation
Functions of HPO axis in an adult female cyclicalMajor aspect of reproductive capacity is its cyclical activity dominant folliclesStrikingly reflected in the growth and development of dominant follicles. single ovulationNormally in human ovaries - a single dominant follicle that results in a single ovulation each menstrual cycle Relationships that underlie folliculogenesis, ovulation, and luteogenesis
Follicular growth is gonadotrophin dependent D1D14D28 Recruitment Dominant OvulationCorpus follicleluteum FSH LH Progesterone P E2
Anovular Subfertility and Male Hypogonadism
Recruitment at a constant rate in first three decades OR reaches a critical number of ~25,000 at 37.5 y Then rate of loss accelerates ~2-fold A decrease in fecundity accompanies this accelerated loss of OR Ovarian reserve Reflected in serum FSH concentration
Two Cell Theory
Follicle selection FSH LH Inhibin Activin E 2 Progesterone Follicular atresia
Climacteric Reproductive decline occurs after third decade Follicular atresia accelerates from 37.5 years Thus reproductive aging precedes the menopause by years Increased FSH & low Inhibin B
Hormonal changes with established menopause Decline in E2 Less marked decline in E1 (peripheral aromatization) E1 higher in obese women In the menopuse E2 < E1
Summary Basis of the H-P-O axis In terms of the life cycle of females Diagnostic relevance
Menopause from Individual Point of View
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