Presentation is loading. Please wait.

Presentation is loading. Please wait.

Hormone Survey: Getting to Know Your Hormones

Similar presentations

Presentation on theme: "Hormone Survey: Getting to Know Your Hormones"— Presentation transcript:

1 Hormone Survey: Getting to Know Your Hormones
Classification of Hormones Classification by System/Function Classification by Source Classification by Structure - Peptide Hormones -Steroid Hormones -Amino Acid Derivatives Classification of Hormone Receptors

2 Some Things to Know about a Hormone
Source (what organ/cell produces and/or secretes it?) What is its target cell(s)? What is the effect on target cells? What regulates its production/secretion? What type of chemical structure? Details of transport/metabolism? What type of receptor/signal transduction?

3 Learning Objectives: Classification of Hormones by Function
Describe the various functions that the endocrine system regulates. Become familiar with the range of hormones involved in these functions. You are NOT responsible for specific names of these hormones yet.

4 Classification of Hormones by Function
Reproductive Hormones: - estrogens (estradiol), androgens (testosterone), progesterone - luteinizing hormone, follicle-stimulating hormone, prolactin, oxytocin - inhibin, activin, follistatin - gonadotropin-releasing hormone

5 Classification of Hormones by Function
Growth Hormones: - Growth hormone (somatotropin) - somatomedins (insulin-like growth factors) - somatostatin, growth hormone-releasing hormone - nerve growth factor, epidermal growth factor, fibroblast growth factor, etc.

6 Classification of Hormones by Function
Hormones regulating carbohydrate/energy metabolism: Insulin, glucagon, cortisol, growth hormone, epinephrine Hormones regulating general body metabolism: - thyroid hormone (T3, T4) - thyroid stimulating hormone (TSH, or thyrotropin) - thyrotropin-releasing hormone (TRH)

7 Classification of Hormones by Function
Hormones involved in stress responses: - norepinephrine, epinephrine - cortisol Hormones involved in mineral and water balance: - aldosterone, renin, vasopressin - atrial natriuretic peptide

8 Classification of Hormones by Function
Regulation of Calcium Metabolism: parathyroid hormone, calcitonin, vitamin D, others…. Regulation of Digestion cholecystokinin, gastrin, secretin, somatostatin Regulation of Blood Formation: erythropoietin, erythrocyte differentiation factor

9 Classification of Hormones by Source
Hypothalamus (brain): acts on the pituitary to control the release of pituitary hormones: -gonadotropin-releasing hormone (GnRH) -thyrotropin-releasing hormone (TRH) -corticotropin-releasing hormone (CRH) -prolactin-inhibiting factor (probably dopamine?) -somatostatin -growth hormone-releasing hormone (GHRH)

10 Classification of Hormones by Source
Anterior Pituitary (anterior lobe): - luteinizing hormone (LH) - follicle-stimulating hormone (FSH) - thyroid-stimulating hormone (TSH) - growth hormone (GH; or somatotropin) - prolactin (PRL) - adrenal corticotropic hormone (ACTH, or corticotropin)

11 Classification of Hormones by Source
Posterior Pituitary (posterior lobe): - oxytocin - vasopressin (antidiuretic hormone, ADH) Intermediate Lobe (absent in adult human): - melanocyte-stimulating hormone

12 Classification of Hormones by Source
Thyroid gland: - thyroid hormones (T3, T4) - calcitonin Parathyroid gland: - parathyroid hormone

13 Classification of Hormones by Source
Ovary and testis: - estrogens, androgens, progesterone - inhibins, activins, follistatin - relaxin Placenta: - human chorionic gonadotropin (hCG) - placental lactogen - steroid hormone

14 Classification of Hormones by Source
Adrenal cortex: - glucocorticoids (cortisol, corticosterone) - mineralocorticoids (aldosterone) - androgens (androstenedione) Adrenal medulla: - epinephrine, norepinephrine

15 Classification of Hormones by Source
Pancreas (endocrine): - insulin - glucagon Kidney: - erythropoietin GI Tract: - gastrin - cholecystokinin - secretin - somatostatin Heart: - atrial natriuretic peptide

16 Reminder…. At this point, do NOT memorize the preceding lists of hormone sources and functions. DO understand the following information on hormone structure….

17 Classification by Structure
Hormones can be classified based on their structure as steroid hormones, peptide hormones, or amino acid derivatives. The structure of the hormone determines: How it is made (gene product; cholesterol derivative; amino acid derivative) How it is transported (binding protein?) How it interacts with receptors on target cells (hormone-receptor interactions)

18 Hormone-Receptor Interactions
Hormones and receptors bind due to noncovalent bonding between them. This also involves a three-dimensional “lock and key” conformation BUT, there is a caveat – this analogy breaks down: Receptor Affinity Receptor Number

19 Hormone-Receptor Interactions
Only specific regions of the hormone and receptor interact. Some regions determine hormone binding Other regions allow signal transduction Small changes in hormone or receptor structure can prevent hormone binding and/or hormone activity

20 Peptide Hormones: Water Soluble Gene Products
Recall that proteins are gene products: gene (DNA) transcription mRNA translation protein

21 Structure of Peptide Hormones
Proteins are made up of amino acids, connected to each other by peptide bonds. Peptide hormones may be very short (three amino acids) to very long (over one hundred amino acids) in length. They typically have an amino terminus (NH2) and a carboxyl terminus (-COOH). NH COOH

22 Structure of Peptide Hormones
Peptides have primary, secondary, tertiary, and quaternary structure:

23 Peptide Hormones: Subunit Structure
Peptide hormones may consist of two subunits joined together, usually by disulfide bonds at cysteine residues. Example: LH, FSH and TSH are composed of a common alpha subunit, and distinct beta subunits: a LHb FSHb TSHb LH FSH TSH

24 Peptide Hormones The shape of peptide hormones may be influenced by and strengthened by disulfide bridges. Peptides may also form ring structures, such as oxytocin.

25 Peptide Hormones: Glycosylation
Peptide hormones may be glycosylated (have carbohydrate side chains). This glycosylation can affect: - assembly of hormone subunits - secretion from the endocrine cell - clearance of the hormone from the circulation - biological activity (receptor binding and biological response of the target cell)

26 Peptide Hormones: Species Homology
The primary amino acid sequence of peptide hormones may differ slightly from species to species. Hormones obtained from one species may not necessarily interact with receptors for hormones of a different species. Example: The human FSH receptor does not respond well to FSH from other species.

27 Endocrine Bioinformatics
Bioinformatics: The utilization of information (ie, databases) to solve biological problems. Example: Suppose you were studying the hormone prolactin, and wanted to see what chromosome it was located on, and if there were any undiscovered hormones which were similar in structure. Approach: Compare the human prolactin sequence to the human genome database at

28 Actions of Peptide Hormones
The effects of peptide hormones are relatively quick, but short-lived. - Anderson et al., 2001

29 Half-life of Peptide Hormones
The half-life of peptide hormones in the circulation is relatively short (water soluble, no binding proteins). - Fares et al., 1992

30 Steroid Hormones Steroid hormones are NOT made up of amino acids. They have a characteristic four ring structure, derived from cholesterol: Examples: estrogens, androgens, progesterone, cortisol, aldosterone

31 Characteristics of Steroid Hormones
Steroid hormones are not glycosylated. The structure of steroid hormones is the same in all species (estradiol in rats is the same as estradiol in humans). Is there a gene for testosterone? How is testosterone made? How is its production regulated?

32 Characteristics of Steroid Hormones
Steroid hormones have more gradual and long-lasting effects than peptide hormones (in general). - Luo et al., 2003

33 Characteristics of Steroid Hormones
Steroid hormones have a relatively longer half life in the circulation (in general, compared with peptide hormones); reflects plasma binding proteins. - Charmandari et al., 2001

34 Amino Acid Derivatives (Amines)
There are other hormones which are not steroids and not peptides, but are derived from amino acid precursors. Epinephrine (adrenaline): Derived from tyrosine.

35 Amino Acid Derivatives
Thyroid hormones (triiodothyronine, thyroxine); are also produced from tyrosine. In this case, get lipid soluble hormones (not water soluble)

36 Water soluble hormones Lipid soluble hormones stimulus gene mRNA
peptide hormones synthesis amino acid derivatives (epinephrine, norepinephrine) stimulus synthesis cholesterol steroid hormone amino acid derivative (thyroid hormone) secretion storage diffusion secretion free hormone free hormone binding protein Hormone Level Hormone Level Time Time plasma membrane receptors ion flux second messengers (cAMP, cGMP) target DNA phosphorylation mRNA protein cellular response cellular response

37 Types of receptors Receptors for the water soluble hormones are found on the surface of the target cell, on the plasma membrane. These types of receptors are coupled to various second messenger systems which mediate the action of the hormone in the target cell. Receptors for the lipid soluble hormones reside in the nucleus (and sometimes the cytoplasm) of the target cell. Because these hormones can diffuse through the lipid bilayer of the plasma membrane, their receptors are located on the interior of the target cell

38 Hormones and their receptors
Class of hormone Location Amine (epinephrine) Water-soluble Cell surface Amine (thyroid hormone) Lipid soluble Intracellular Peptide/protein Water soluble Steroids and Vitamin D Lipid Soluble

39 Second messenger systems
Receptors for the water soluble hormones are found on the surface of the target cell, on the plasma membrane. These types of receptors are coupled to various second messenger systems which mediate the action of the hormone in the target cell

40 Second messengers for cell-surface receptors
Second messenger systems include: Adenylate cyclase which catalyzes the conversion of ATP to cyclic AMP; Guanylate cyclase which catalyzes the conversion of GMP to cyclic GMP (cyclic AMP and cyclic GMP are known collectively as cyclic nucleotides); Calcium and calmodulin; phospholipase C which catalyzes phosphoinositide turnover producing inositol phosphates and diacyl glycerol.

41 Types of receptors

42 Second messenger systems
Each of these second messenger systems activates a specific protein kinase enzyme. These include cyclic nucleotide-dependent protein kinases Calcium/calmodulin-dependent protein kinase, and protein kinase C which depends on diacyl glycerol binding for activation. Protein kinase C activity is further increased by calcium which is released by the action of inositol phosphates.

43 Second messenger systems
The generation of second messengers and activation of specific protein kinases results in changes in the activity of the target cell which characterizes the response that the hormone evokes. Changes evoked by the actions of second messengers are usually rapid

44 Signal transduction mechanisms of hormones
Activation of adenylate cyclase Inhibition of adenylate cyclase Increased phospho-inositide turnover Tyrosine kinase activation b-adrenergic a2-adrenergic a1-adgrenergic Insulin LH, FSH, TSH, hCG Opioid Angiotensin II Growth factors (PDGF, EGF, FGF, IGF-1 Glucagon Muscarinic cholinergic – M2 Muscarinic cholinergic – M3 Growth hormone Vasopressin- V2 Vasopressin –V1 Prolactin ACTH

45 Cell surface receptor action

46 G-protein coupled receptors
Adenylate cyclase, cAMP and PKA

47 Amplification via 2nd messenger

48 Transmembrane kinase-linked receptors
Certain receptors have intrinsic kinase activity. These include receptors for growth factors, insulin etc. Receptors for growth factors usually have intrinsic tyrosine kinase activity Other tyrosine-kinase associated receptor, such as those for Growth Hormone, Prolactin and the cytokines, do not have intrinsic kinase activity, but activate soluble, intracellular kinases such as the Jak kinases. In addition, a newly described class of receptors have intrinsic serine/threonine kinase activity—this class includes receptors for inhibin, activin, TGFb, and Mullerian Inhibitory Factor (MIF).

49 Protein tyrosine kinase receptors

50 Receptors for lipid-soluble hormones reside within the cell
Because these hormones can diffuse through the lipid bilayer of the plasma membrane, their receptors are located on the interior of the target cell. The lipid soluble hormone diffuses into the cell and binds to the receptor which undergoes a conformational change. The receptor-hormone complex is then binds to specific DNA sequences called response elements. These DNA sequences are in the regulatory regions of genes.

51 Receptors for lipid-soluble hormones reside within the cell
The receptor-hormone complex binds to the regulatory region of the gene and changes the expression of that gene. In most cases binding of receptor-hormone complex to the gene stimulating the transcription of messenger RNA. The messenger RNA travels to the cytoplasm where it is translated into protein. The translated proteins that are produced participate in the response that is evoked by the hormone in the target cell Responses evoked by lipid soluble hormones are usually SLOW, requiring transcription/translation to evoke physiological responses.

52 Mechanism of lipid soluble hormone action

53 Receptor control mechanisms
Hormonally induced negative regulation of receptors is referred to as homologous-desensitization This homeostatic mechanism protects from toxic effects of hormone excess. Heterologous desensitization occurs when exposure of the cell to one agonist reduces the responsiveness of the cell any other agonist that acts through a different receptor. This most commonly occurs through receptors that act through the adenylyl cyclase system. Heterologous desensitization results in a broad pattern of refractoriness with slower onset than homologous desensitization

Download ppt "Hormone Survey: Getting to Know Your Hormones"

Similar presentations

Ads by Google