SA Medical - General Medicine And Imaging of Disease

Female Hormonal system: Gonadotropin-releasing hormone (GnRH) from the hypothalamus that stimulates FSH and LH secretion from the anterior pituitary. GnRH is inhibited by circulating estrogen and progesterone LH is secreted from the basophillic cells of the anterior pituitary gland and stimulates the development of the corpus luteum in the ovaries. FSH  is secreted from the basophillic cells of the anterior pituitary gland in response to GnRH and stimulates the follicles in the ovaries. Estrogen and Progesterone are the steroid hormones secreted by the follicle and corpus luthium of the ovary.  Corpus luteum x Section of the ovary. 1. Outer covering. 1’. Attached border. 2. Central stroma. 3. Peripheral stroma. 4. Bloodvessels. 5. Vesicular follicles in their earliest stage. 6, 7, 8. More advanced follicles. 9. An almost mature follicle. 9’. Follicle from which the ovum has escaped. 10.  Corpus luteum . Monthly Menstrual or Ovarian Cycle Follicular Development At th

Spermatogenesis Sper mato genesis is the process of formation of spermatocytes from spermatogonia Sper minog enesis is the process of transformation of the spermatids, which are still epitheloid to sperm cells Male Sex Hormones Testosterone is an anabolic steroid hormone secreted by Leydig cells of the testis Gonadotropin-releasing hormone increases release of the LH and FSH from the anterior pituitary gland LH stimulates testosterone formation by the Leydig Cells, and FSH stimulates sperm ato genesis and sperm ino genesis Inhibin is forced by Sertoli cells and inhibits FSH secretion The Male Sexual Act Male Infertility Androgen dysfunction with normal sperm cell production Isolated dysfunction of sperm cell production with normal androgen levels Combined androgen and sperm cell production defects MALE REPRODUCTIVE PHYSIOLOGY A. Testes Structure and Function 1. Seminiferous tubules 2. Sert

There are 2 regulatory hormones, Parathyroid Hormone and calcitonin. CALCIUM AND PHOSPHATE IN THE EXTRACELLULAR FLUID AND THE PLASMA FUNCTION OF VITAMIN D. CONTROL OF VITAMIN D FORMATION The active form of Vitamin D 1,25-dihydroxycholecalceferol is regulated via the following steps In the skin: 7-dehyrocholesterol is conveted by UV light to Vitamin D3 In the liver:  Vitamin D3 is converted to 25-hydroxycholecalciferol In the cortex of the kidney:  25-hydroxycholecalciferol is converted to 1,25-dihydroxycholecalceferol in reaction stimulated and controlled by PTH. PTH formation is stimulated by a reduction in ECF Calcium concentration, formation of 1,25-dihyroxycholecalcepherol also increases when Calium concentration in the ECF drops GASTROINTESTINAL CALCIUM ABSORPTION - 1,25-DIHYDROXYCHOLECALCIFEROL stimulates the intestinal epithelium of the small intestine to form calcium binding protein, calcium stimulated ATPase and Alkaline phosphatase, all which promote absor

Three basic patterns of endocrine pathologies: Hormone excess, Hormone deficiency, and abnormal responsiveness of target tissues to a hormone. CRH-ACTH-Cortisol-Target Tissue-Response Hypersecretion Exaggerates a Hormones Effects Adenomas may cause hypersecretion. Tumours, including non-endocrine tumours may secrete hormones. Exogenous source of hormones, eg Exogenous Cortisol. Prolonged use may cause cellular atrophy. Hyposecretion Diminishes or Eliminates a Hormones Effects Most commonly due to atrophy of the endocrine gland. Adrenal Gland atrophy secondary to tuberculosis, diminishing cortisol production Receptor or Second Messenger Problems Cause Abnormal Tissue Responsiveness Downregulation Hyperinsulinemia - sustained levels of insulin cause the insulin receptors of target tissues to remove insulin receptors from the cell membrane. Patients suffering from hyperinsulinemia show signs of diabetes despite their high insulin levels. Receptor and Signal Transduction

Hormones act together, facilitate one another or against each other. In synergism , the Effect if Interacting hormones is more than additive Glugagon, Cortisol and Epinephrine increase the blood glucose levels - Their combined effect is more than additive, the epinepharine potentiates the glucogon's effect on blood glucose,  Augmentin is an example of synergism A permissive hormone allows another hormone to exert its full effect Permissiveness, if thyroid is not present the maturation of the reproductive system is delayed. Tyroid cannot by itself stimulate sexual maturation of the reproductive system, tyroid hormone is considered permissive. Anatgonistic hormones have opposing effects Competitive inhibition or antagonists Glucagon and Growth Hormone, both release glucose are antagonists to Insulin. Growth hormone decreases  the number of insulin receptor,  providing functional antagonism to insulin.