Topic 4 - Endocrinology

Question 1

Steroid hormones are lipid soluble.

Answer 1

True

Question 2

Steroid hormones directly activate ion channels.

Answer 2

False

Steroid hormones are lipid signalling molecules that act mainly by altering gene transcription.

Question 3

Steroid hormones can alter gene transcription.

Answer 3

True

Question 4

Steroid hormones are secreted as they are synthesised.

Answer 4

True

As they are lipids they cannot be stored in membrane-bound vesicles and therefore are secreted as they are synthesised.

Question 5

Hypothalamic releasing hormones are synthesized and secreted by neurons.

Answer 5

True

Question 6

Blood flows from the anterior pituitary to the hypothalamus in portal vessels.

Answer 6

False

Blood flows from the hypothalamus to the anterior pituitary gland via the hypothalamo-hypophyseal portal system.

Question 7

The hypothalamic releasing hormones reach the general circulation in significant amounts.

Answer 7

False

Although the releasing hormones are secreted into the portal system, negligible quantities reach the general circulation.

Question 8

Loss of dopaminergic neurons in the hypothalamus is likely to lead to a rise in the secretion of prolactin.

Answer 8

True

Question 9

Growth hormone secretion is regulated by a single hypothalamic hormone.

Answer 9

False

Dopamine acts as an inhibitory hormone on the pituitary lactotrophs that secrete prolactin. GH secretion is under the control of both somatostatin and GHRH. The latter hormone increases GH secretion.

Question 10

A 10-year-old child in whom anterior pituitary function is deficient is likely to: Have a low basal metabolic rate.

Answer 10

True

Deficient anterior pituitary function will lead to low TSH levels and so thyroid hormone secretion will be depressed, leading to a reduction in BMR.

Question 11

A 10-year-old child in whom anterior pituitary function is deficient is likely to: Develop acromegaly.

Answer 11

Fasle

Acromegaly is a disorder characteristic of hypersecretion of GH in adults.

Question 12

A 10-year-old child in whom anterior pituitary function is deficient is likely to: Be of short stature but have relatively normal body proportions.

Answer 12

True

Deficient secretion of GH in childhood results in pituitary dwarfism in which body proportions are normal.

Question 13

A 10-year-old child in whom anterior pituitary function is deficient is likely to: Be in constant danger of becoming dehydrated.

Answer 13

False

Lack of ADH from the posterior pituitary increases the risk of dehydration.

Question 14

A 10-year-old child in whom anterior pituitary function is deficient is likely to: Become sexually mature at a later age than normal.

Answer 14

True

Lack of pituitary gonadotrophins will lead to delay or failure of sexual maturation due to lack of stimulation of the gonads.

Question 15

Chromaffin cells are found in the adrenal medulla.

Answer 15

True

Chromaffin cells are found in the adrenal medulla as well as in some other locations.

Question 16

Excess secretion of catecholamines will lead to hypertension.

Answer 16

True

The catecholamines increase heart rate (and acetylcholine released by the parasympathetic postganglionic fibers decreases heart rate).

Question 17

The heart rate is reduced by circulating epirephrine and norepinephrine.

Answer 17

False

Epinephrine and norepinephrine raise arterial blood pressure through their actions on both the heart and vasculature.

Question 18

Increased catecholamine secretion stimulates lipolysis.

Answer 18

True

Catecholamines activate lipases which mobilize fats to increase the production of free fatty acids and glycerol.

Question 19

Epinephrine and norepinephrine are secreted by the adrenal cortex.

Answer 19

False

Epinephrine and norepinephrine are secreted by the adrenal medulla.

Question 20

Normal plasma levels of PTH stimulate osteoblast activity.

Answer 20

True

When plasma calcium levels are normal, PTH secretion stimulates bone formation through its action on osteoblasts (cells which secrete bone matrix).

Question 21

PTH decreases calcium excretion from the body.

Answer 21

True

Question 22

PTH directly increases calcium absorption by the gut.

Answer 22

False

While PTH stimulates calcium absorption by the renal tubules, it has no direct action on the gut. However, it does stimulate the production of 1,25-dihy-droxycholecalciferol, which stimulates calcium absorption from the gut.

Question 23

PTH is secreted in response to elevated plasma calcium levels.

Answer 23

False

Low plasma calcium levels stimulate PTH secretion; high plasma levels stimulate the secretion of calcitonin.

Question 24

High levels of circulating PTH demineralize bone and elevate plasma calcium.

Answer 24

True

When PTH levels are elevated, osteoclast activity is stimulated which leads to the demineralization of bone and release of calcium into the plasma.

Question 25

Oxytocin stimulates the synthesis of milk by the mammary glands.

Answer 25

False

Oxytocin stimulates the ejection of milk from the lactiferous ducts. Synthesis of milk is controlled by prolactin.

Question 26

Lack of ADH will result in excessive production of urine.

Answer 26

True

In the absence of ADH, very little water is reabsorbed by the collecting ducts of the kidney, leading to the production of a large volume of dilute urine.

Question 27

Both oxytocin and ADH are secreted in response to neuro-endocrine reflexes.

Answer 27

True

Oxytocin is released in response to the mechanical stimulus of suckling while ADH is released in response to changes in the volume and osmolality of the plasma, which are detected by specific receptors.

Question 28

The secretion of oxytocin and ADH are regulated by releasing hormones secreted by the hypothalamus.

Answer 28

False

The releasing hormones regulate the secretion of hormones from the anterior pituitary.

Question 29

ADH acts by binding to receptors on the plasma membrane of cells in the collecting ducts.

Answer 29

True

ADH exerts its actions by binding to G protein-coupled V2 receptors on the P-cells of the collecting ducts.

Question 30

The adrenal cortex secretes both peptide and steroid hormones.

Answer 30

False

All the hormones secreted by the adrenal cortex are steroids.

Question 31

The adrenal cortex will atrophy following removal of the anterior pituitary gland.

Answer 31

True

Pituitary ACTH acts to maintain the structural integrity and function of the adrenal cortex.

Question 32

Aldosterone plays a role in the regulation of plasma calcium.

Answer 32

False

Aldosterone plays an important role in the regulation of plasma SODIUM and thereby in the regulation of total body water.

Question 33

The secretion of cortisol peaks at around 6 a.m. each day.

Answer 33

True

Cortisol secretion shows a circadian rhythm that is controlled by ACTH release from the anterior pituitary. Secretion is at its lowest around midnight and rises to a peak around dawn. It then declines during the course of the day.

Question 34

Cortisol is a hyperglycemic hormone.

Answer 34

True

Cortisol stimulates gluconeogenesis and maintains reserves of glycogen for use in periods of fasting.

Question 35

Thyroid hormones are essential for the early development and maturation of the central nervous system.

Answer 35

True

Lack of TH in fetal and early neonatal life leads to a condition called cretinism in which there is mental retardation.

Question 36

T3 and T4 stimulate the secretion of TSH by the anterior pituitary.

Answer 36

False

Thyroid hormones inhibit the secretion of TSH by negative feedback

Question 37

People who have an underactive thyroid gland have a low BMR.

Answer 37

True

Thyroid hormones stimulate metabolism and when TH levels are low, BMR is reduced.

Question 38

A resting pulse rate of 65 b.p.m would suggest a diagnosis of thyrotoxicosis.

Answer 38

False

Thyrotoxicosis is caused by an overactive thyroid gland. High levels of TH will increase BMR and elevate the heart rate. The value given is normal.

Question 39

Most of the iodide in the body is present in the thyroid gland.

Answer 39

True

The thyroid gland avidly takes up iodine and incorporates it into thyroglobulin.