Question 1 Hypothalamic hormones which regulate the synthesi

Question 1) Hypothalamic hormones which regulate the synthesis and secretion of anterior pituitary hormones include all of the following EXCEPT A. TRH (thyrotropin releasing hormone) B. GnRH (gonadotropin releasing hormone) C. somatomedin c D. somatostatin E. CRH (corticotrophin releasing hormone)

Question 2) All of the following statements regarding the second messenger concept of hormone action are true EXCEPT which one? A. The hormone itself is the first messenger. B. Hormones act through receptors to stimulate the production of the second messenger. C. Cyclic AMP is a leading candidate for the second messenger of lipid-soluble hormones such as steroids. D. None of the above are exceptions; all statements are true.

Solution

1) Somatomedin.

All these hormones act on the anterior pituitary and regulate synthesis and secretion of the hormones produced by it but not all are produced by hypothalamus, somatomedin is produced by liver which travels in the blood to act upon the anterior pituitary to regulate the release of somatostatin from hypothalamus.

2. The hormones are first messengers as in they bind to the receptors of the target cell to exert their effect. The binding of the hormones to its receptor leads to activation of a signal transduction pathway where a cascade of the reaction takes place in which a second messenger like cAMP is produced through the action of adenylate cyclase. This cAMP takes the initial signal further into the cell and regulate cell actvity for example by moving into the nucleus and regulating gene expression. This differs in the case of steroid lipid soluble hormones because these steroids can cross the lipid bilayer due to its lipophilic nature. Once inside the cell they bind to the nuclear receptors giving a hormone-receptor complex which moves in to the nucleus to regulate gene expression of target genes.

So, C is an exception.