Question 1

An elderly person becomes confused and takes an overdose of a medication designed to block both cholesterol uptake from the GI tract and cholesterol synthesis by all cells.After 24 hours,the individual is severely hypocholesterolemic (i.e.,has very low levels of circulating cholesterol).This effect is transient: as the effects of the drug wear off,hormone levels rebound.Which of the following is most responsible for stability of hormone levels in this situation?

Accepted Answer

The most likely mechanism responsible for stability of hormone levels in this situation is negative feedback loop. The decrease in circulating cholesterol levels would lead to an increase in hormone synthesis, triggering a negative feedback loop that would ultimately result in stability of hormone levels. Other choices (hepatic turnover, peripheral conversion, renal excretion, and melatonin) are not directly related to the stability of hormone levels in this situation.

Question 2

An elderly person becomes confused and takes an overdose of a medication designed to block both cholesterol uptake from the gastrointestinal (GI)tract and cholesterol synthesis by all cells.After 24 hours,the individual is severely hypocholesterolemic (i.e.,has very low levels of circulating cholesterol).This individual would exhibit a transient lower level of which type of hormone?

Accepted Answer

Steroid hormones are derived from cholesterol, so a severe hypocholesterolemic state would lead to a temporary decrease in the production of steroid hormones. Catecholamines, protein hormones, iodothyronines, and peptide hormones are not directly derived from cholesterol and would not be affected by this medication.

Question 3

Many pituitary hormones are secreted in a circadian rhythm.A structure important in the regulation of circadian hormonal rhythms is:

Accepted Answer

The suprachiasmatic nucleus is a structure located in the hypothalamus that plays a key role in regulating circadian rhythms, including the secretion of pituitary hormones. It receives input from the retina to synchronize its activity with the external environment, and then sends signals to other brain regions and the rest of the body to coordinate the timing of various physiological processes.

Question 4

Hormones act through binding to their receptors.Which of following hormones binds only to a receptor located on the cell membrane?

Accepted Answer

Catecholamines (such as epinephrine and norepinephrine) bind to receptors located on the cell membrane, while thyroid hormone, estrogen, progesterone, and vitamin D bind to receptors located within the cell (either in the cytoplasm or nucleus).

Question 5

Endocrine glands are organs dedicated to making hormones.Some organs make hormones but have other important functions.An example of such a hormone-producing organ that is not considered a dedicated endocrine gland is:

Accepted Answer

The liver produces hormones such as insulin-like growth factor (IGF) and angiotensinogen, but it is not considered a dedicated endocrine gland as it also has other important functions such as detoxification and synthesis of bile.

Question 6

Many hormones are synthesized as preprohormones.A mutation in a preprohormone-encoding gene that changed the amino acid sequence of the signal peptide could result in:

Accepted Answer

The signal peptide is necessary for targeting the preprohormone to the endoplasmic reticulum (ER) where it will be processed and cleaved into the mature hormone. Without a functional signal peptide, the preprohormone cannot be properly translocated into the ER and will likely be degraded or stuck in the cytoplasm, resulting in an inability of the hormone to be secreted.

Question 7

An important process that can activate a steroid hormone or even change a steroid hormone into a different type of hormone (e.g.,changing an androgen molecule into an estrogen molecule)is called:

Accepted Answer

Peripheral conversion is the process by which a steroid hormone is activated or transformed into a different type of hormone. This process often involves enzymatic reactions that occur in peripheral tissues such as adipose tissue, the liver, or the gonads. For example, androgen hormones can be converted into estrogen hormones through peripheral conversion in adipose tissue or the gonads.

Question 8

Endocrine diseases are often due to loss of hormone (i.e.,a hormone deficiency).Which of the following would cause an endocrine disease that mimicked a protein hormone deficiency without a deficiency in the levels of a circulating protein hormone?

Accepted Answer

A defective receptor would prevent the hormone from exerting its effects, mimicking a hormone deficiency, even though the hormone levels are normal.

Question 9

Protein hormones are secreted in a regulated manner,through a mechanism referred to as:

Accepted Answer

Protein hormones are secreted in response to a specific stimulus, such as a change in blood glucose levels or the presence of a hormone-releasing hormone. This process is called stimulus-secretion coupling, and it ensures that hormones are released into the bloodstream only when they are needed. Constitutive secretion, on the other hand, is the continuous release of proteins from cells without regulation. Endocytosis recycling, signal peptidase-induced cleavage, and membrane shedding are not mechanisms involved in the regulation of protein hormone secretion.

Question 10

The hypothalamus has an important role in the hypothalamic-pituitary-endocrine gland axes.As part of these axes,hypothalamic neuroendocrine neurons secrete:

Accepted Answer

The hypothalamic-pituitary-endocrine gland axes involve the secretion of releasing hormones from hypothalamic neuroendocrine neurons, which then stimulate the pituitary gland to release various hormones that regulate the activity of other endocrine glands in the body. Tropic hormones, such as adrenocorticotropic hormone (ACTH) and follicle-stimulating hormone (FSH), are examples of pituitary hormones that stimulate the activity of other endocrine glands. Steroid hormones and thyroid hormones are not typically secreted by hypothalamic neuroendocrine neurons.

Quiz 38: Introduction to the Endocrine System