Endocrinology Summers

Hormones Endocrine Glands Receptors Homeostasis 2nd Messengers

Nuclear Receptors Genetic Regulation Hormone Synthesis Receptor Regulation Hypothalamo-Hypophysial Communication

Tropic Hormones Neurohypophysial Nonapeptides Thyroid Axis Steroids Adrenal Axis

Adrenal Medulla Osmotic-Pressure Balance Reproductive Endocrinology Prolactin Somatic Axis

Growth Factors Immune Factors Ca++, PO4 Homeostasis Pancreatic Hormones GI Hormones

Guts 'n Brains Brain Hormones Neurosteroids Neuropeptides Endocrine Evolution

Figures for Endocrionology text:Vertebrate Endocrinology5th Edition - David O. Norris and James A. Carr: Read pages 107-119, 124-134, 163-164, 187-203 for this lecture acronyms    end

XI. Tropic Hormones 	

	A. 3 categories


		1. glycoprotein hormones


			a. adenohypophysial: LH, FSH, TSH


			b. chorionic or placental: CG (gonadotropin) and CT (thyrotropin)


				i. hCG refers to human chorionic gonadotropin


				
		2. large, single polypeptide chains


			a. adenohypophysial: GH, PrL


			b. chorionic: CS (somatomammotropin) = PL (placental lactogen)


			
		3. small single peptide chains


			a. adenohypophysial (pars distalis): ACTH, LPH, endorphins


				i. pars intermedia: a-MSH


			b. chorionic: POMC, ACTH

			
			
		4. Release of all tropic hormones facilitated by PACAP

		
		
	B. Glycoprotein hormones

		1. 2 polypeptide subunits

			a. a subunit chains identical
			
				i. same a for LH or FSH or TSH


			b. b chain specific to each hormone

				i. responsible for unique biological activity

					(1) separate subunits have little activity


			c. each chain with a carbohydrate attached

			d. weight ~32,000 daltons

			

		2. Luteinizing Hormone (LH)


			a. a gonadotropin


			b. stimulates production and secretion of
			   androgens, estrogens and progestins


			c. Chorionic Gonadotropin (CG)


				i. very similar in  b chain structure and biological activity


				ii. Pregnant Mare Serum Gonadotropin (PMSG = eCG)


				iii. stimulates steroidogenesis, maintains ovaries


			d. LH causes ovulation and formation of the corpus luteum 
			  (luteinization)

				i. normal [CG] will not cause ovulation
				
				ii. LH stimulates spermiation 


		3. FSH (follicle stimulating hormone)

			a. a gonadotropin


			b. stimulates spermatogenesis in the testes and
			   follicular growth in the ovary


			c. contributes to steroidogenesis in the gonads


		4. TSH

			a. stimulates production and release of thyroid hormones 

				i. T4 (thyroxine)and T3 (tri-iodothyronine)


	C. Growth Hormone and Prolactin


		1. Growth Hormone

			a. anabolic

			b. 191 aa, 21,500 daltons

			c. liberation of somatomedins (like IGF1) from plasma proteins and
			    stimulation of growth factor production


		2. Prolactin

			a. similar in structure to GH, 199 aa


			b. lactogenic, many other effects


		3. Chorionic Somatomammotropin (CS or PL = placental lactogen)

			a. some GH but mostly PRL activity


			b. structural homologies to both, 191 aa: 1-161 identical to GH

			

	D. hormones from POMC (Pro - Opio - Melano - cortin)


		1. ACTH = corticotropin - 39 aa


			a. stimulates glucocorticoid (B/F) secretion


		2.  a-MSH - 13 aa


			a. stimulates melanin dispersion


		3. Endorphins - 31 aa for   b-endorphin


			a. opioid/pain killing action


			b. enkephalins and dynorphins


		4. Lipotropin - 58 or 91 aa


			a. lipolysis, other POMC fragments are weakly lipolytic