| PRL, T4, ANF, ADH, CCK, Testosterone, Erythropoietin, Thymosin  | 
		
| A: | Compared to a bull, a bullock is docile because of lower levels of testosterone | 
| B: | The thyroid gland hormones play an important role in the development and maturation of the central nervous system | 
| 1. | Is a steroid hormone and generates second messengers | 
| 2. | Cannot cross lipid bilayer as it is a water-soluble hormone | 
| 3. | Is an iodothyronine | 
| 4. | Cannot cross the cell membrane as it is a lipid-soluble hormone | 
| 1. | ACTH is a steroid hormone | 
| 2. | PTH can enter the nucleus of bone cells whereas ACTH cannot | 
| 3. | The membranes of bone cells contain receptors different from those in adrenocortical cells | 
| 4. | Bone releases a protein that inhibits the action of ACTH |