Endocrinology, lecture on Tropic Hormones
USD Department of Biology
Endocrine Glands
2nd Messengers
Nuclear Receptors
Genetic Regulation
Hormone Synthesis
Receptor Regulation
Hypothalamo-Hypophysial Communication
Tropic Hormones
Neurohypophysial Nonapeptides
Thyroid Axis
Adrenal Axis
Adrenal Medulla
Osmotic-Pressure Balance
Reproductive Endocrinology
Somatic Axis
Growth Factors
Immune Factors
Ca++, PO4 Homeostasis
Pancreatic Hormones
GI Hormones
Guts 'n Brains
Brain Hormones
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 

				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

XII. Neurohypophysial Nonapeptides