Thyroxine and triiodothyronine:
1. are synthesized by stratified cuboidal epithelial cells called follicular cells
2. are very soluble in water and therefore easily soluble in the bloodstream
3. are synthesized and secreted by parafollicular cells
4. are ultimately formed from the amino acid, L-tyrosine

All the following regarding parathyroid glands are true except:

The beta cells of the endocrine pancreas secrete insulin that:
1. is secreted by the alpha cells of the pancreas
2. promotes the entry of glucose and amino acids into tissue cells
3. promotes the breakdown of glycogen (glycogenolysis) and fat (lipolysis)
4. falls in level immediately after a meal is eaten

Melatonin is the hormone that regulates wakefulness. Which of the following does not correctly characterize melatonin?
1. It is secreted by the pineal gland, the gland located in the roof of the third ventricle.
2. Its secretion is highest in children aged one to five and decreases thereafter.
3. It may have an important role in the onset of puberty.
4. More is secreted in the daytime than at night.

The human placenta has endocrine functions that does not secrete:
1. prolactin
2. estrogens
3. progesterones
4. human chorionic gonadotropin (HCG)

Cortisol, estrogen, progesterone, androgens and aldosterone:
1. are derived from cholesterol molecules
2. are polar molecules
3. include the prostaglandins and the sex hormones testosterone and progesterone
4. bind mostly to receptors in the cell membrane

Identify the non steroidal hormones that are nonpolar and can be administered orally:
1. prostaglandins
2. estrogen and progesterone
3. insulin and glucagon
4. thyroid hormones (T₃ and T₄)

All the following regarding regulation of a physiological function by either a neurotransmitter or a hormone are true except:

1. Target cells must have specific receptor proteins with which these molecules combine.
2. When these molecules bind to target cells, specific sequences of changes must occur.
3. There must be an "off-switch" that will stop the induced changes.
4. Second messengers will always be involved in the response of the target cell.

Synergism between hormones can be best described as:
1. Two or more hormones working together to produce a particular result.
2. One hormone is needed to enhance the responsiveness of an organ to a second hormone.
3. Either of the hormones does not act alone.
4. The effects of the two hormones are opposite to each other.

What would not be true for steroid hormones like corticosteroids?

1. Steroids are lipids with complex ring structures.
2. Steroids can pass through their target cell membrane and interact with receptors in the nucleus.
3. Steroids employ first and second messengers that amplify the cellular response.
4. The estrogens and testosterone are examples of steroid hormones.