Semester 2 - Endocrine - Hypothalamic And Pituitary Physiology And Pharmacology

1. A 35-year-old woman presented to the clinic complaining of continuous thirst and polyuria. She had had a basal skull fracture following a car accident six month previously from which she recovered completely. She reported that she often awoke at night because of thirst and a need to urinate. Urinalysis showed a urine osmolality of 2O mOsm/Kg and undetectable plasma ADH levels. Which if the following drugs would be appropriate for the patient?

Hydrochlorothiazide

Amiloride

Desmopressin

Carbamazepine

Chlorpropamide

The woman's symptoms of continuous thirst and polyuria, along with undetectable plasma ADH levels and low urine osmolality, suggest that she is experiencing central diabetes insipidus. Desmopressin, a synthetic form of ADH, would be appropriate for this patient as it can help to reduce excessive thirst and urine production by replacing the deficient ADH. Hydrochlorothiazide, Amiloride, Carbamazepine, and Chlorpropamide are not indicated for central diabetes insipidus and would not address the underlying cause of the patient's symptoms.

Explanation

The woman's symptoms of continuous thirst and polyuria, along with undetectable plasma ADH levels and low urine osmolality, suggest that she is experiencing central diabetes insipidus. Desmopressin, a synthetic form of ADH, would be appropriate for this patient as it can help to reduce excessive thirst and urine production by replacing the deficient ADH. Hydrochlorothiazide, Amiloride, Carbamazepine, and Chlorpropamide are not indicated for central diabetes insipidus and would not address the underlying cause of the patient's symptoms.

2. By which of the following mechanisms does bromocriptine relieve symptoms of hyperprolactinemia in a patient with prolactin-secreting pituitary adenoma?

Blocking prolactin receptors

Blocking receptors for prolactin releasing hormone

A cytotoxic effect on pituitary adenoma cells

Stimulating dopamine receptors

Stimulating serotonin receptors

Bromocriptine relieves symptoms of hyperprolactinemia in a patient with prolactin-secreting pituitary adenoma by stimulating dopamine receptors. Dopamine inhibits the release of prolactin from the pituitary gland. By stimulating dopamine receptors, bromocriptine decreases the production and release of prolactin, thereby reducing the symptoms associated with hyperprolactinemia.

Explanation

Bromocriptine relieves symptoms of hyperprolactinemia in a patient with prolactin-secreting pituitary adenoma by stimulating dopamine receptors. Dopamine inhibits the release of prolactin from the pituitary gland. By stimulating dopamine receptors, bromocriptine decreases the production and release of prolactin, thereby reducing the symptoms associated with hyperprolactinemia.

3. Both the anterior and posterior pituitary glands depend upon input from hypothalamic nuclei for release of pituitary hormones. In the following table which row correctly lists the type of connections between the hypothalamus and the anterior and posterior pituitary glands?

.	Hypothalamus to anterior pituitary	Hypothalamus to posterior pituitary
A	Axonal connections	Axonal connections
B	Releasing factors	Releasing factors
C	Axonal connections	Releasing factors
D	Releasing factors	Axonal connections

A

B

C

D

The correct answer is D. The explanation is that the hypothalamus releases releasing factors that travel through the bloodstream to the anterior pituitary gland, where they stimulate the release of specific hormones. This is known as the hypothalamus to anterior pituitary releasing factors pathway. On the other hand, the hypothalamus has direct axonal connections with the posterior pituitary gland, allowing it to release hormones directly into the bloodstream. Therefore, the correct answer is D, as it correctly lists the type of connections between the hypothalamus and the anterior and posterior pituitary glands.

Explanation

The correct answer is D. The explanation is that the hypothalamus releases releasing factors that travel through the bloodstream to the anterior pituitary gland, where they stimulate the release of specific hormones. This is known as the hypothalamus to anterior pituitary releasing factors pathway. On the other hand, the hypothalamus has direct axonal connections with the posterior pituitary gland, allowing it to release hormones directly into the bloodstream. Therefore, the correct answer is D, as it correctly lists the type of connections between the hypothalamus and the anterior and posterior pituitary glands.

4. The presence of a tumor in the anterior pituitary causes a decrease in ACTH secretion. Which of the following correctly describes changes in plasma levels of hormones?

Increased CRH, increased ACTH, and increased cortisol

Decreased CRH, decreased ACTH, and decreased cortisol

Increased CRH, decreased ACTH, and decreased cortisol

Increased CRH, increased ACTH, and decreased cortisol

Decreased CRH, decreased ACTH, and increased cortisol

When a tumor is present in the anterior pituitary, it can disrupt the normal secretion of hormones. In this case, the tumor causes a decrease in ACTH secretion. ACTH is responsible for stimulating the production of cortisol. Therefore, with decreased ACTH levels, there will be a decrease in cortisol levels as well. However, to compensate for the decreased ACTH, the body may increase the production of CRH (corticotropin-releasing hormone) in an attempt to stimulate ACTH secretion. So, the correct answer is Increased CRH, decreased ACTH, and decreased cortisol.

Explanation

When a tumor is present in the anterior pituitary, it can disrupt the normal secretion of hormones. In this case, the tumor causes a decrease in ACTH secretion. ACTH is responsible for stimulating the production of cortisol. Therefore, with decreased ACTH levels, there will be a decrease in cortisol levels as well. However, to compensate for the decreased ACTH, the body may increase the production of CRH (corticotropin-releasing hormone) in an attempt to stimulate ACTH secretion. So, the correct answer is Increased CRH, decreased ACTH, and decreased cortisol.

5. A 3O-year-old man who suffered a head injury presented one month after recovery with excessive thirst and urination. After examination and lab tests he was diagnosed with neurogenic diabetes insipidus. Desmopressin was prescribed to him. Which of the following is its mechanism of action?

It stimulatesV2 receptors

It prevents the breakdown of ADH

It stimulate the release of ADH from posterior pituitary

It stimulates V1 receptors

Desmopressin is a synthetic form of vasopressin, also known as antidiuretic hormone (ADH). It works by specifically stimulating V2 receptors in the kidneys, which increases water reabsorption and reduces urine production. This helps to alleviate the excessive thirst and urination symptoms associated with neurogenic diabetes insipidus.

Explanation

Desmopressin is a synthetic form of vasopressin, also known as antidiuretic hormone (ADH). It works by specifically stimulating V2 receptors in the kidneys, which increases water reabsorption and reduces urine production. This helps to alleviate the excessive thirst and urination symptoms associated with neurogenic diabetes insipidus.

6. A 28 year-old woman attends her doctor because she has not had a menstrual cycle of two months, but commercial pregnancy tests have proven negative. She reports that a few weeks before her expected menstrual cycle was missed, she had suffered an accident in a gaffe, in which she had fallen from a climbing rope" head first" onto some weight-training equipment, and sustained bruising on the left side of her face around her cheek, eye and temples. The woman reports that following the accident she had noticed that she was feeling continually fatigued, and had gained weight. She feels thirsty most of the time and is perplexed as to why she needs to urinate more often than before. Physical examination confirms that the woman is not. pregnant and reveals traces of a white crystalline deposit around her nipples. The level of which hormone would be expected to be elevated in the plasma of this patient?

Luteinizing Hormone (LH)

Thyroid Stimulating Hormone (TSH)

Follicle Stimulating Hormone (FSH)

Oxytocin

Prolactin (Prl)

The correct answer is Prolactin (Prl). Prolactin is a hormone produced by the pituitary gland that is responsible for stimulating milk production in the breasts. In this case, the presence of a white crystalline deposit around the patient's nipples suggests that she may be experiencing galactorrhea, which is the abnormal production of breast milk. This, along with her other symptoms such as missed periods, fatigue, weight gain, increased thirst, and frequent urination, are consistent with hyperprolactinemia, which is an elevated level of prolactin in the blood.

Explanation

The correct answer is Prolactin (Prl). Prolactin is a hormone produced by the pituitary gland that is responsible for stimulating milk production in the breasts. In this case, the presence of a white crystalline deposit around the patient's nipples suggests that she may be experiencing galactorrhea, which is the abnormal production of breast milk. This, along with her other symptoms such as missed periods, fatigue, weight gain, increased thirst, and frequent urination, are consistent with hyperprolactinemia, which is an elevated level of prolactin in the blood.

7. A 23-year old male patient comes to your office who is 3 feet 6 inches tall. your initial diagnosis is that an endocrine disorder accounts for his short stature. To confirm your diagnosis you run a series of laboratory tests. The laboratory results come back with the following findings: 1) plasmaIGF-1levels are extremely low, 2) plasma GH levels are very high, and 3) exogenous GHRH elicits a further increase in GH. What would be the most likely defect in this individual to explain his dwarfism?

Excessive production of somatostat in by periventricular hypothalamic neurons.

Inadequate production of GHRH by arcuate neurons of the hypothalamus

Inadequate production of IGF-1 by somatotrophs of the anterior pituitary gland.

Overproduction of GHRH by arcuate neurons of the hypothalamus.

Inability of the liver to produce IGF-1.

The most likely defect in this individual to explain his dwarfism is the inability of the liver to produce IGF-1. This is supported by the laboratory findings of extremely low plasma IGF-1 levels. IGF-1 is a hormone that is produced by the liver in response to growth hormone (GH) stimulation. In this case, the high plasma GH levels indicate that there is adequate production of GH, but the absence of IGF-1 suggests that the liver is not able to convert GH into IGF-1.

Explanation

The most likely defect in this individual to explain his dwarfism is the inability of the liver to produce IGF-1. This is supported by the laboratory findings of extremely low plasma IGF-1 levels. IGF-1 is a hormone that is produced by the liver in response to growth hormone (GH) stimulation. In this case, the high plasma GH levels indicate that there is adequate production of GH, but the absence of IGF-1 suggests that the liver is not able to convert GH into IGF-1.

8. A 35-year-old man presented to the hospital with a history of joint pain, headache, excessive sweating, and deepening of the voice. A physical examination revealed protrusion of the jaw, enlargement of the hands, thickening of the skin, and a barrel chest. A CT scan disclosed a pituitary adenoma and the patient underwent radiotherapy. Which of the following drugs was most likely prescribed while waiting for radiotherapy to work?

Leuprolide

Cosyntropin

Somatropin

Octreotide

Protirelin

Octreotide is a synthetic somatostatin analog that is commonly prescribed in patients with pituitary adenomas. It helps to suppress the excessive secretion of growth hormone from the pituitary gland, which is often the cause of the symptoms described in the patient. By reducing the production of growth hormone, octreotide can help alleviate the joint pain, headache, excessive sweating, and deepening of the voice. It is typically prescribed while waiting for radiotherapy to work, as it takes time for the effects of radiotherapy to become noticeable.

Explanation

Octreotide is a synthetic somatostatin analog that is commonly prescribed in patients with pituitary adenomas. It helps to suppress the excessive secretion of growth hormone from the pituitary gland, which is often the cause of the symptoms described in the patient. By reducing the production of growth hormone, octreotide can help alleviate the joint pain, headache, excessive sweating, and deepening of the voice. It is typically prescribed while waiting for radiotherapy to work, as it takes time for the effects of radiotherapy to become noticeable.

9. Which drug for treating acromegaly acts by blocking receptors for growth hormone?

Somatropin

Pegvisomant

Octreotide

Sermorelin

Cabergoline

Pegvisomant is the correct answer because it acts by blocking receptors for growth hormone. This drug is used in the treatment of acromegaly, a condition characterized by excessive growth hormone production. By blocking the receptors, pegvisomant helps to reduce the effects of excess growth hormone in the body. Other options such as somatropin, octreotide, sermorelin, and cabergoline do not specifically block growth hormone receptors and are not commonly used for treating acromegaly.

Explanation

Pegvisomant is the correct answer because it acts by blocking receptors for growth hormone. This drug is used in the treatment of acromegaly, a condition characterized by excessive growth hormone production. By blocking the receptors, pegvisomant helps to reduce the effects of excess growth hormone in the body. Other options such as somatropin, octreotide, sermorelin, and cabergoline do not specifically block growth hormone receptors and are not commonly used for treating acromegaly.

10. Although the production of IGF-1 by the liver makes an important contribution to circulating levels of IGF-1,many other tissues produce IGFs. For most tissues,IGF-1 is considered to act as what type of signaling factor?

Hormone

Paracrine

Autocrine

Intracrine

Neuroendocrine

IGF-1 is considered to act as a paracrine signaling factor in most tissues. Paracrine signaling occurs when a cell releases signaling molecules that act on nearby cells, rather than being transported through the bloodstream to distant target cells. In the case of IGF-1, it is produced by various tissues and acts locally on neighboring cells to regulate their growth and development.

Explanation

IGF-1 is considered to act as a paracrine signaling factor in most tissues. Paracrine signaling occurs when a cell releases signaling molecules that act on nearby cells, rather than being transported through the bloodstream to distant target cells. In the case of IGF-1, it is produced by various tissues and acts locally on neighboring cells to regulate their growth and development.

11. A 25-year-old male patient comes to a local clinic with the following complaints. He has to urinate frequently and he is constantly drinking water. A 24-urine collection is taken with the following findings. Urine volume is 6 liters per day and the specific gravity of the urine is 1.005 (normal range is 1.010-1.025j.ysur te_ntative diagnosis is diabetes insipidus. You administer intravenously an analogue of vasopressin and observe that the subsequent 24 hour urine collection is reduced to 3 liters per day. What is the most likely explanation for his polyuria?

Aquatrophs of the anterior pituitary are not being stimulated by vasopressin releasing hormone.

V1 receptors on epithelial cells of the collecting tubules and ducts are absent.

V2 receptors on epithelial cells of the collecting

The most likely explanation for the patient's polyuria is that the magnocellular neurons of the Para ventricular and suproptic nuclei of the hypothalamus are not responding to an increase in whole body osmolarity and are not releasing vasopressin from the posterior pituitary. This is supported by the fact that administering an analogue of vasopressin reduces the urine volume, indicating that the lack of vasopressin release is causing the excessive urine production.

Explanation

The most likely explanation for the patient's polyuria is that the magnocellular neurons of the Para ventricular and suproptic nuclei of the hypothalamus are not responding to an increase in whole body osmolarity and are not releasing vasopressin from the posterior pituitary. This is supported by the fact that administering an analogue of vasopressin reduces the urine volume, indicating that the lack of vasopressin release is causing the excessive urine production.

12. A 48 YO man with a family history of heart disease has followed a heart-healthy lifestyle for fifteen years. Despite these efforts he has recently experienced unusual fatigue and lightheadedness , especially when rising suddenly. Physical examination, demonstrates postural hypotension and a darker-than usual complexion for midwinter in the Midwest (he works and exercises indoors). Lab work reveals that he is hyponatremic, . hyperkalemic, and hypocalcemic Further blood tests are ordered to assay plasma corticotropin-releasing hormone(CRH), corticotropin (ACTH), and cortisol. What combination of hyper and/or hyposecretion for these hormones would be the most likely given this man's signs and symptoms?

.	CRH secretion	ACTH secretion	Cortisol secretion
A	Hyper-secretion	Hyper-secretion	Hyper-secretion
B	Hyper-secretion	Hyper-secretion	Hypo-secretion
C	Hyper-secretion	Hypo-secretion	Hypo-secretion
D	Hypo-secretion	Hypo-secretion	Hypo-secretion
E	Hypo-secretion	Hypo-secretion	hyper-secretion

A

B

C

D

E

Given the patient's signs and symptoms, the most likely combination of hyper and/or hyposecretion for these hormones would be hyper-secretion of CRH, hyper-secretion of ACTH, and hypo-secretion of cortisol. This is because the patient is experiencing postural hypotension and a darker-than-usual complexion, which could be caused by low cortisol levels. Additionally, the patient is hyponatremic, hyperkalemic, and hypocalcemic, which could be caused by excessive secretion of CRH and ACTH. Therefore, option B is the correct answer.

Explanation

Given the patient's signs and symptoms, the most likely combination of hyper and/or hyposecretion for these hormones would be hyper-secretion of CRH, hyper-secretion of ACTH, and hypo-secretion of cortisol. This is because the patient is experiencing postural hypotension and a darker-than-usual complexion, which could be caused by low cortisol levels. Additionally, the patient is hyponatremic, hyperkalemic, and hypocalcemic, which could be caused by excessive secretion of CRH and ACTH. Therefore, option B is the correct answer.

13. While doing a pediatric rotation, you observe a visit by 10-year-old male patient who is below the 1Oth percentile for height. The pediatrician makes an initial diagnosis of dwarfism caused by pituitary dysfunction. However, the physician asks you to develop a strategy to determine if the actual cause is growth hormone receptor dysfunction. Laboratory values for serum growth hormone were above normal. Which of the following would constitute a key piece of information in your diagnostic strategy?

Low plasma levels of growth hormone binding protein

Low plasma levels of IGF-1

Elevated plasma levels for growth hormone releasing hormone

Decreased plasma levels of somatostatin

A key piece of information in the diagnostic strategy would be low plasma levels of growth hormone binding protein. Growth hormone binding protein is responsible for binding to growth hormone and transporting it to target tissues. If there are low levels of growth hormone binding protein, it indicates that there may be a dysfunction in the growth hormone receptor, as the binding protein is necessary for the proper functioning of the receptor. This supports the suspicion that the patient's condition is caused by growth hormone receptor dysfunction rather than pituitary dysfunction.

Explanation

A key piece of information in the diagnostic strategy would be low plasma levels of growth hormone binding protein. Growth hormone binding protein is responsible for binding to growth hormone and transporting it to target tissues. If there are low levels of growth hormone binding protein, it indicates that there may be a dysfunction in the growth hormone receptor, as the binding protein is necessary for the proper functioning of the receptor. This supports the suspicion that the patient's condition is caused by growth hormone receptor dysfunction rather than pituitary dysfunction.

14. A 19 YO man decides to begin a vegan diet, but he fails to adequately compensate for the nutritional content of the dairy products in his former diet, so his intake of calcium drops dramatically. Which of the following hormones' direct actions will be most important in the maintenance of his plasma calcium?

Insulin

Thyroid hormone

Calcitonin

1,25-dihyroxycholecalciferol

Parathyroid hormone

When the man fails to adequately compensate for the nutritional content of dairy products in his former diet, his intake of calcium drops dramatically. In order to maintain his plasma calcium levels, the most important hormone would be 1,25-dihydroxycholecalciferol. This hormone, also known as active vitamin D, helps in the absorption of calcium from the intestines and promotes its reabsorption from the kidneys. It also stimulates the release of calcium from the bones when needed. Therefore, in this situation, 1,25-dihydroxycholecalciferol would play a crucial role in maintaining the man's plasma calcium levels.

Explanation

When the man fails to adequately compensate for the nutritional content of dairy products in his former diet, his intake of calcium drops dramatically. In order to maintain his plasma calcium levels, the most important hormone would be 1,25-dihydroxycholecalciferol. This hormone, also known as active vitamin D, helps in the absorption of calcium from the intestines and promotes its reabsorption from the kidneys. It also stimulates the release of calcium from the bones when needed. Therefore, in this situation, 1,25-dihydroxycholecalciferol would play a crucial role in maintaining the man's plasma calcium levels.