Hypothalamic-Pituitary Physiology

Question 1

What does the posterior pituitary regulate as part of the hypothalamus-pituitary complex (2)?

Answer 1

Lactation

Water metabolism

Question 2

What does the anterior pituitary regulate as part of the hypothalamus-pituitary complex (4)?

Answer 2

Thyroid gland

Adrenal glands

Reproductive glands

Somatic growth

Question 3

What is the function of the hypothalamus?

Answer 3

Collect and integrate signals and funnel them to the pituitary gland.

Question 4

Where does the pituitary lie?

Answer 4

In a depression of the sphenoid bone called the sella turcica.

Question 5

Why are vision problems (mainly peripheral vision) associated with tumors of the pituitary?

Answer 5

Tumors cause the pituitary to be pushed upward, compressing the optic nerves at the optic chiasm

Question 6

Where are the anterior and posterior pituitaries derived from? What are their technical names?

Answer 6

Rathke’s pouch (oral ectoderm) grows upward into the adenohypophysis

Neural down growth from the diencephalon (infundibulum) gives rise to the neurohypophysis

Question 7

What are the six hormones secreted by the hypothalamus to the adenohypophysis?

Answer 7

Growth hormone-releasing hormone (GHRH)

Thyroid-releasing hormone (TRH)

Corticotropin-releasing hormone (CRH)

Gonadotropin-releasing hormone (GnRH)

Dopamine (DA)

Somatostatin (SST)

Question 8

The supraoptic nucleus secretes what hormone to the neurohypophysis?

Answer 8

Oxytocin

Question 9

The paraventricular nucleus secretes what hormone to the neurohypophysis?

Answer 9

Antidiuretic hormone (ADH/vasopressin)

Question 10

What are the five cell types of the adenohypophysis and what six peptide hormones do they secrete?

Answer 10

Lactotrophs: prolactin (PRL)

Somatotrophs: growth hormone (GH)

Corticotrophs: (ACTH)

Gonadotrophs: follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Thyrotrophs: thyroid-stimulating hormone (TSH)

Question 11

Somatostatin and dopamine are inhibiting hormones of the hypothalamus and pituitary. What do they inhibit?

Answer 11

Somatostatin: GH and TSH

Dopamine: PRL

Question 12

Releasing hormones are secreted into what structure?

Answer 12

Median eminence

The first capillary bed in the hypophyseal portal system

Question 13

Long-acting GnRH analogs (leuprolide) have been used in the treatment of what (4)? How do they work?

Answer 13

Treats:

Precocious puberty

Manipulation of reproductive cycles (IVF)

Treatment of endometriosis

PCOS

Acts as an agonist to GnRHr to decrease gonadotropin as well as sex hormones

Question 14

What are some factors that can lead to hyperprolactinemia? (4)

Answer 14

Drugs that block dopamine (D2 receptors)

Lesions that interfere with portal blood flow

Primary hyperthyroidism (high TRH)

Lactotroph adenomas (prolactinomas; ~40% of all pituitary tumors)

Question 15

What are the two primary actions of prolactin?

Answer 15

Enhanced breast development during pregnancy

Induce lactogenesis

Question 16

What are the symptoms caused by prolactinomas? Men? Women? Both?

Answer 16

Both: headache, visual disturbance, hypopituitarism

Women: loss of menstrual periods, breast milk reduction, acne, excessive body/facial hair

Men: erectile dysfunction, enlarged breasts, diminished sexual interest

Question 17

How many amino acids long is prolactin?

Answer 17

99

Question 18

How many amino acids long is growth hormone? What other special characteristic does it have?

Answer 18

191 amino acids longs

2 disulfide bridges

Question 19

What is the function of growth hormone after puberty is complete?

Answer 19

Modulate metabolism, body composition, and functional capabilities

Question 20

What are the direct and indirect effects of GH?

Answer 20

Direct: GH binds to its receptor on target cells (ex: lipolysis in adipocytes)

Indirect: mediated by insulin-like growth factor-1 (IGF-1), which is secreted from the liver in response to growth hormone (ex: bone growth)

Question 21

What pituitary hormone is an antagonist for GHRH?

Answer 21

Somatostatin

Question 22

What are the effects of GH? (4)

Answer 22

*Postnatal growth of bones (cartilage in epiphyseal plates)

Increases organ size and fucntion

Increase lean body mass and decreases fat cell size

Increase blood glucose concentration

Question 23

What is the average rate of secretion of GH? When does it peak?

Answer 23

~10 pulses/day

Regular nocturnal peak (deep sleep)

Question 24

At approximately what rate do GH levels drop over the course of a lifetime?

Answer 24

~50% drop every 7 years

Question 25

What conditions can cause a decrease in GH secretion? (3)

Answer 25

Obesity

Non-alcoholic fatty liver disease (NAFLD)

Type 2 diabetes

Question 26

What disorder is caused by GH deficiency before puberty?

Answer 26

Dwarfism:

Retarded skeletal growth

Delayed sexual development

Poorly developed muscles

Excess subcutaneous fat

Question 27

What disorder is caused by a resistance to GH due to dysfunction of the GH receptor?

Answer 27

Laron syndrome

350 cases worldwide

Autosomal recessive

Patients do not grow past 4 feet but are very well protected against cancer, diabetes, and potentially heart diseases and Alzheimer’s

Question 28

Why is GH deficiency difficult to diagnose in adults?

Answer 28

“generic” symptoms

reduced well-being

increased fat mass (central obesity)

Dyslipidemia

Increased cardiovascular disease

Decreased bone density

Question 29

What disorder is caused by an increase in GH before puberty (before closure of epiphyseal plates)? Symptoms? Life expectancy?

Answer 29

Gigantism:

Glucose intolerance and hyperinsulinism

Cardiovascular problems

More susceptible to infections

30-40 year life expectancy

Question 30

What disorder is caused by an increase in GH after puberty? Symptoms? Treatment?

Answer 30

Acromegaly:

Enlargement of hands, feet, forehead, jaw, nose, and heart (oppositional growth)

Thick skin and large tongue

Treatment: surgery or somatostatin analogs