Lecture 9 - The Gonads 2 Flashcards
List three androgens
Androstenedione - weak Testosterone Dihydrotestosterone (DHT)
What can testosterone be synthesised to?
Via Reduction (5 alpha reductase) - DHT Via Aromatisation (Aromatase) - 17BO
Where does the synthesis of DHT occur?
Prostate, testes, seminiferous tubules, seminal vesicles, skin, brain, adenohypophysis
Where does the synthesis of 17BO occur?
Adrenals, testes, Sertoli cells, liver, skin, brain
What is the main method of DHT transport in the BLOOD?
Sex hormone binding globulin - 60% (Albumin - 38% and FREE - 2%)
What is the main method of DHT transport in the SEMINIFEROUS FLUID?
Androgen binding globulin - bioactive
What actions do androgens have on a fetus?
Develop internal and external genitalia
General growth - males believed to be bigger at birth as androgens ^ growth
Behavioural characteristics
What actions do androgens have on adults?
Spermatogenesis
Growth and development of male genitalia, 2ry sex glands (prostate), 2ry sex characteristics
Protein anabolism
Pubertal growth spurt with GH
Behavioural effects
Feedback regulation
NB: some androgenic effects mediated by turning into oestrogen
Define oestrogens
Any substance that induces mitosis in the endometrium
Give examples of oestrogens
17BO (MAIN ONE in menstrual cycle) - POTENT Oestrone (precursor) - WEAK Oestriol (MAIN ONE in pregnancy) - WEAK
What are the principal actions of oestrogens, to do with reproductive characteristics?
Stimulate proliferation of endometrium Maturation of follicle during follicular phase Induction of LH surge -> ovulation Effects on vagina/cervix Stimulates growth of ductile system in breast Decreases sebaceous gland secretion
What are the principal actions of oestrogens to do with whole body?
^ salt (and water) reabsorption ^ plasma protein synthesis - influences enzymes Metabolic actions - ^ HDL levels Stimulates osteobalsts Influences release of other hormones - prolactin, thyrotrophin Behavioral effects Feedback regulation - +VE and -VE
Define progestogens
Any substance that induces secretory changes in the endometrium
Give examples of progestogens
Progesterone - precursor in steroidal synthesis pathway 17 alpha-hydroxyprogesterone - small amounts released at points during menstrual cycle
What are the principal actions of progestogens?
Stimulate secretory activity in endometrium/cervix/vagina Stimulates growth of alveolar system in breast Decreased renal NaCl reabsorption (competitive inhibition of aldosterone) Increase in basal body temperature Negative feedback regulation