Objectives

Learning Objectives 4

Overview of Biochemical Endocrinology

1. Define hormone and receptor and identify associated properties, both chemically and with respect to their biochemical and physiological significance.

2. Identify the lipophilic hormones that bind to intracellular receptors and the hydrophilic amine and peptide hormones that bind to the cell surface.

3. Identify the second messengers that are associated with specific hormones and specific types of receptors.

4. Describe the general mechanism of signal transduction via G-proteins.

5. Discuss the process leading to the production of IP₃ and DAG, and the general mechanism of action of these second messengers.

Vitamin A and Vision

1. Identify provitamin A / b-carotene, vitamin A / retinol, vitamin A ester / retinol palmitate, retinaldehyde / retinal and retinoic acid (all-trans and 9-cis) in terms of their positions on the pathway of vitamin A metabolism. Delineate which reactions are reversible and which are not.

2. Describe the biological function of each of the forms of vitamin A.

3. Outline the actions of noncovalent vitamin A binding proteins including: RBP, CRBP, CRABP, RAR and RXR.

4. Describe the role of vitamin A in the visual cycle, in particular the roles played by: retinal isomerase, opsin, rhodopsin, metarhodopsin, transducin, cGMP, phosphodiesterase, Na²⁺, Ca²⁺, recoverin, rhodopsin kinase, arrestin.

5. Define progressive vitamin A deficiency clinically and biochemically.

6. Discuss why excess vitamin A is toxic to skin, bones, liver and gut.

7. Classify vitamin A and its RAR with the ligands for PPAR, the thyroid hormone receptor (TR) and the vitamin D receptor (VDR).

Neurobiochemistry I: Pituitary / Hypothalamus

1. Identify the molecular etiologies of diabetes insipidus.

2. Define the chemistry of ADH/vasopressin and oxytocin, and develop that they are coded for by related genes which also code for their respective neurophysin carriers.

3. Describe how the secretion of ADH/vasopressin and oxytocin is controlled at the physiological and biochemical levels.

4. Discuss the mechanism whereby ADH/vasopressin controls water channels in the cells of the distal convoluted tubules of the kidney.

5. List the actions of oxytocin, including CNS effects, and differentiate how a number of neuromodulator peptides induce a desired behavior which coordinates with their systemic functions.

6. List the hypothalmic releasing and inhibiting factors and explain the biochemical mechanism, including second messengers, in general terms.

7. Diagram the proposed model for the effects of GHRH and somatostatin on adenylate cyclase.

Neurobiochemistry II: Growth Hormone / Prolactin

1 Discuss the close chemical relationship between growth hormone (GH) and prolactin (PRL), as well as between their receptors.

2. List the actions of GH and define which ones are mediated by IGF-I.

3. Compare and contrast IGF-I and insulin, especially with respect to their receptors and how tissues differentially respond to these two similar peptides.

4. Distinguish that the IGF-I receptor is a tyrosine kinase in the insulin receptor family, while the PRL and GH receptors do not posses this activity and must recruit cytoplasmic tyrosine kinases called JAK's.

5. Discuss the tissue specific distribution of GH receptor.

6. Identify the biochemical actions of PRL and its interrelationship to estrogen function.