Endocrine Reproduction Introduction Dr. Mohammed Kalimi Endocrine Reproduction Introduction

Biosynthesis of hormones: The peptide hormones are synthesized by rough endoplasmic reticulum as a pre-pro-hormone The steroid and amine hormones are synthesized from cholesterol and tyrosine respectively through a series of enzymatic reactions by smooth endoplasmic reticulum, and mitochondria

Release of hormone Excitation secretion coupling and release ↑ Intracellular calcium ↑ cAMP ↑ Activation of microtubular or microfilament system ↑ Fusion of membrane of the secretory granule with that of the cell ↑ Ejection of the hormone by exocytosis

Hormone release Secretion rate or production rate of a hormone: n moles / minute or ng / minute Plasma concentration of a hormone: n moles / mL or ng / mL

Transport of hormones in blood: Bound to carrier proteins: Steroid and thyroid hormones circulate bound to specific globulins Unbound or free: With few exceptions (IGF-I), peptides and protein hormones circulate unbound

Inactivation of hormones: By specific target tissues (internalization and lysosomal degradation) By liver and kidneys By both of the above

Measurement of hormones: Radioimmunoassay Localization of hormones in tissues of origin and action: Immunocytochemistry

Control of hormonal secretion Positive or Negative Feedback Neuro-Endocrine Integration Neuronal Control (dopaminergic, adrenergic,cholinergic) Sleep-wake cycle, menstrual cycle, diurnal rhythm

Major function of hormones: Initiates, mediates and regulates the processes of growth, differentiation, development, maturation and aging Maintenance of homeostasis, fluid and electrolyte balance (Na+, K+, Ca++, glucose, water ) Regulation of cellular metabolism (fats, carbohydrates, proteins) Sexual development and function, lactation and behavior

Malfunctioning of the endocrine system: Primarily caused by: Overproduction of a hormone (hyperfunction) Underproduction of a hormone (hypofunction) Unresponsiveness of target organ (lack of receptor, etc.) Production of abnormal hormone

Neuroendocrinology Similarities between the two: Each synthesizes and releases specific chemical agents which are capable of influencing another cell by interacting with specific receptors Both neurons and endocrine cells generate electrical potentials and can be depolarized

Neuroendocrinology Differences between the two: Nervous system: Specific chemical agents released are disseminated only a very short distance System is fast acting Actions are relatively short-lived Operates with point to point precision Affects only glandular secretions and muscular contractions

Neuroendocrinology Endocrine system: Specific chemical agents are released and carried via the blood stream throughout the whole body System is slow acting Actions are relatively long-lived Affects a whole variety of cell types

Hypothalamus Thyroid-stimulating-hormone-releasing-hormone (TRH) Corticotrophin-releasing-hormone (CRH) Luteinizing-hormone-releasing-hormone (LHRH) Growth-hormone-releasing-hormone (GHRH) Somatostatin Dopamine

Anterior Pituitary Hormones Growth Hormone (GH) Prolactin Thyroid Stimulating Hormone (TSH) Adrenocorticotrophic Hormone (ACTH) Luteinizing Hormone (LH) Follicle Stimulating Hormone (FSH) Melanocyte stimulating Hormone (MSH)

Posterior Pituitary Hormones Oxytocin Vasopressin or Anti Diuretic Hormone (ADH)

TH Gland Thyroid Hormones (T3 and T4): Follicular cells Calcitonin : Parafollicular cells

Adrenal Cortex Glucocorticoids : Cortisol and Corticosterone Aldosterone

Para Thyroid Gland PTH

Adrenal Medulla Epinephrine and Norepinephrine

Pancreas Insulin Glucagon Somatostatin

Skin, Liver, and Kidney Vitamin D

Gonads Testis: Testosterone Ovaries: Estrogen, Progesterone

Placenta Human Chrionic Gonadotropin (hCG) Human Placental Lactogen (hPL)

Steroid Hormone Mechanism Estrogens Androgens Progesterone Aldosterone Glucocorticoids Thyroid Hormones Vitamin D Vitamin A

Cyclic AMP ( cAMP) Mechanism LH FSH TSH ACTH ADH (via V2 Receptor) hCG MSH CRH Catecholamines Calcitonin Glucagon PTH

cAMP Inhibitory ( cAMP) mechanism Somatostatin Dopamine

The Calcium-Phospholipid mechanism GnRH (LHRH) TRH Angiotensin II ADH via the V1 receptor

Associated Tyrosine Kinase mechanism (Janus Kinase) Prolactin GH

Intrisic tyrosine phospho-kinase mechanism Insulin IGF-I

Hypothalamus Calcium-Phospholipid Mechanism TRH, LHRH ↑Adenylyl Cyclase, ↑cAMP Mechanism CRH,GHRH Adenylyl Cyclase,cAMP Mechanism Somatostatin Dopamine

Anterior Pituitary Hormones Janus Kinase (associated tyrosine kinase) Mechanism GH, Prolactin ↑ cAMP Mechanism TSH, LH, FSH, ACTH, MSH

Posterior Pituitary Hormones Calcium-Phospholipid Mechanism Oxytocin, ADH (via V1 receptor) ↑cAMP Mechanism ADH (via V2 receptor)

↑ cAMP mechanism Adrenal Medulla Epinephrine and Norepinephrine Parathyroid Gland PTH TH Gland (Parafollicular Cells) Calcitonin Pancreas (α Cells) Glucagon Placenta hCG