Department of Physiology: Endocrine Physiology-Critical thinking

1. The hypothalamo-hypophysial portal system connects the hypothalamus with the anterior pituitary. Why is such a special circulatory system advantageous?

2. A patient exhibits polydipsia (thirst), polyuria (excess urine production), and urine with a low specific gravity (contains few ions and no glucose). If you wanted to reverse the symptoms, would you administer insulin, glucagon, ADH, or aldosterone? Explain.

3. A patient complains of headaches and visual disturbances. A casual glance reveals enlarged finger bones, a heavy deposition of bone over the eyes, and a prominent jaw. The doctor determines that the headaches and visual disturbances result from increased pressure within the skull and that the presence of a pituitary tumor is affecting hormone secretion. Name the hormone causing the problem, and explain why increased pressure exists within the skull.

4. Most laboratories are able to determine blood levels of TSH, T3, and T4. Given that ability, design a method of determining whether hyperthyroidism in a patient results from a pituitary abnormality or from the production of a non-pituitary thyroid stimulatory substance.

5. Over the past year, Julie has gradually gained weight. The increase in adipose tissue is distributed over her trunk, face, and neck and her muscle mass appear to be decreased. Julie also feels weak and bruises easily. Her physician suspects Cushing syndrome and orders a series of blood tests. The results reveal elevated blood levels of cortisol and ACTH. There is no evidence of an extra-pituitary source of ACTH. Predict the cause of Julie’s condition and the treatments that are likely to be recommended.

6. An anatomy and physiology instructor asks two students to predict a patient’s response to chronic vitamin D deficiency. One student claims the person would suffer from hypocalcemia. The other student claims the calcium levels would remain within their normal range, although at the low end, and that bone reabsorption would occur to the point that advanced osteomalacia might occur. With whom do you agree, and why?

7. A patient arrives at the emergency room in an unconscious condition. A medical emergency bracelet reveals that he has diabetes. The patient is in either diabetic coma or insulin shock. How can you tell which, and what treatment do you recommend for each condition?

8. Predict some of the consequences of exposure to intense and prolonged stress.

9. Katie was getting nervous. At 16, she was the only one in her group of friends who had not started menstruating. Katie had always dreamed of having three beautiful children someday and she was worried. Her mother took her to see Dr. Josephine, who ordered several blood tests. When the results came back, Dr. Josephine gently explained to Katie and her mother that Katie would never be able to have children and would never menstruate. Dr. Josephine then asked Katie to wait in the outer room while she spoke privately to her mother. She explained to Katie’s mom that Katie has androgen insensitivity syndrome. Though Katie is genetically male and her gonads produce more of the male reproductive hormone, testosterone, than the female reproductive hormone, estrogen, Katie did not reflect the tissue changes expected. What malfunction in Katie’s body would cause this? Why does Katie’s body look feminine if she is genetically male?

10. Why would males with testicular feminization syndrome be unusually tall?

11. If an adult male were castrated (testes were removed), what would happen to the levels of GnRH, FSH, LH, and testosterone in his blood? What effect would these hormonal changes have on his sex characteristics and sexual behavior?

12. If a 9-year-old boy were castrated, what would happen to the levels of GnRH, FSH, LH, and testosterone in his blood? What effect would these hormonal changes have on his sex characteristics and sexual behavior as an adult?

13. Suppose you want to produce a birth control pill for men. On the basis of what you know about the male hormone system, what process should the pill affect? Discuss any possible side effects of the pill.

14. If the ovaries are removed from a postmenopausal woman, what happens to the levels of GnRH, FSH, LH, estrogen, and progesterone in her blood? What symptoms would you expect to observe?

15. If the ovaries are removed from a 20-year-old woman, what happens to the levels of GnRH, FSH, LH, estrogen, and progesterone in her blood? What side effects would these hormonal changes have on her sex characteristics and sexual behavior?

16. A study divides healthy women into two groups (A and B). Both groups are composed of women who have been sexually active for at least 2 years and are not pregnant at the beginning of the experiment. The subjects weigh about the same amount, and none smokes cigarettes, although some drink alcohol occasionally. Group A women receive a placebo in the form of a sugar pill each morning of their menstrual cycles. Group B women receive a pill containing estrogen and progesterone each morning of their menstrual cycles. Then plasma LH levels are measured before, during, and after ovulation. The results are as follows: The number of pregnancies in group A is 37/100 women/year. The number of pregnancies in group B is 1.5/100 women/year. What conclusion can you reach on the basis of these data? Explain the mechanism involved.

17. A woman who is taking birth control pills that consist of only progesterone experiences the hot flashes of menopause. Explain why.

18. GnRH can be used to treat some women who want to have children but have not been able to get pregnant. Explain why it is critical to administer the correct concentration of GnRH at the right time during the menstrual cycle.

19. Dr. Procter has two patients, one of whom has elevated blood PSA. A digital exam reveals that both patient 1 and patient 2 have enlarged prostate glands. Patient 1’s enlarged prostate has the same shape as a smaller prostate, except that it is larger than normal, with a smooth contour. Patient 2’s prostate is enlarged and asymmetrical, with a rough contour. In what way are these patients’ lives probably being affected by their enlarged prostates? Explain how the doctor was able to conclude that one of the patients is likely to have prostate cancer.

20. Diane has peritonitis (an inflammation of the peritoneum), which her physician says resulted from a urinary tract infection. Why might this condition occur more readily in females than in males?

21. In a condition known as endometriosis, endometrial cells are believed to migrate from the body of the uterus into the uterine tubes or by way of the uterine tubes into the peritoneal cavity, where they become established. A major symptom of endometriosis is periodic pain. Why does such pain occur?

22. Contraceptive pills contain estradiol and progesterone, or progesterone alone, administered at programmed doses during the ovarian cycle to prevent follicle maturation and ovulation. Explain how such pills are effective.

23. Female bodybuilders and women with eating disorders such as anorexia nervosa commonly experience amenorrhea. What does this fact suggest about the relation between body fat and menstruation? What effect would amenorrhea have on achieving a successful pregnancy?

24. Roger has been extremely thirsty. He drinks numerous glasses of water every day and urinates a great deal. Name two disorders that could produce these signs and symptoms. What test could a clinician perform to determine which disorder Roger has?

25. Julie is pregnant but is not receiving prenatal care. She has a poor diet consisting mostly of fast food. She drinks no milk, preferring colas instead. How would this situation affect Julie’s level of parathyroid hormone?

26. Sherry tells her physician that she has been restless and irritable lately. She has a hard time sleeping and complains of diarrhea and weight loss. During the examination, her physician notices a higher-thannormal heart rate and a fine tremor in her outstretched fingers. What tests could the physician perform to make a positive diagnosis of Sherry’s condition?

27. What are two benefits of having a portal system connect the median eminence of the hypothalamus with the anterior lobe of the pituitary gland?

28. Pamela and her teammates are considering taking testosterone supplements (anabolic steroids) to enhance their competitive skills. What natural effects of this hormone are they hoping to gain? What additional side effects might these women expect should they begin an anabolic steroid regime?

29. Roger has been extremely thirsty. He drinks numerous glasses of water every day and urinates a great deal. Name two disorders that could produce these signs and symptoms. What test could a clinician perform to determine which disorder Roger has?

30. Julie is pregnant but is not receiving prenatal care. She has a poor diet consisting mostly of fast food. She drinks no milk, preferring colas instead. How would this situation affect Julie’s level of parathyroid hormone?

31. Sherry tells her physician that she has been restless and irritable lately. She has a hard time sleeping and complains of diarrhea and weight loss. During the examination, her physician notices a higher-than-normal heart rate and a fine tremor in her outstretched fingers. What tests could the physician perform to make a positive diagnosis of Sherry’s condition?

32. What are two benefits of having a portal system connect the median eminence of the hypothalamus with the anterior lobe of the pituitary gland?

33. Pamela and her teammates are considering taking testosterone supplements (anabolic steroids) to enhance their competitive skills. What natural effects of this hormone are they hoping to gain? What additional side effects might these women expect should they begin an anabolic steroid regime?

34. Roger has been extremely thirsty. He drinks numerous glasses of water every day and urinates a great deal. Name two disorders that could produce these signs and symptoms. What test could a clinician perform to determine which disorder Roger has?

35. Julie is pregnant but is not receiving prenatal care. She has a poor diet consisting mostly of fast food. She drinks no milk, preferring colas instead. How would this situation affect Julie’s level of parathyroid hormone?

36. Sherry tells her physician that she has been restless and irritable lately. She has a hard time sleeping and complains of diarrhea and weight loss. During the examination, her physician notices a higher-than-normal heart rate and a fine tremor in her outstretched fingers. What tests could the physician perform to make a positive diagnosis of Sherry’s condition?

37. What are two benefits of having a portal system connect the median eminence of the hypothalamus with the anterior lobe of the pituitary gland?

38. Pamela and her teammates are considering taking testosterone supplements (anabolic steroids) to enhance their competitive skills. What natural effects of this hormone are they hoping to gain? What additional side effects might these women expect should they begin an anabolic steroid regime?

39. Blood tests are a way to diagnose any number of endocrine disorders because hormones are transported by the circulatory system. GH and IGF-1 can be checked to determine if def ciencies are the reason for a child’s slow growth. Blood levels of TSH, T3, and T4 provide information about thyroid function. Some tests, such as the glucose tolerance test from the chapter opener, do not directly measure the level of the glucose-regulating hormones (in this case, insulin) but rather indirectly monitor whether an endocrine gland is performing correctly by measuring specific compounds in the blood. A. How is follicle-stimulating hormone similar to growth hormone with regard to how their target cells respond to their signals? B. It is possible to diagnose hypothyroidism by high levels of TSH in the blood. Explain what would cause a high TSH level. (Hint: You may want to consider what happens to TSH when the activity of the thyroid is normal.) C. Why would a diabetic urinate frequently and always be thirsty? D. Many diets advertise that they are specifically designed for diabetics. How would these diets be different from a “normal” diet?

40. Twenty-three-year-old Monica and her husband Bill are ready to start a family. They are both avid bicyclists and weight-lifters who carefully watch what they eat and pride themselves on their “buff” bodies. However, Monica is having difficulty becoming pregnant. Monica hasn’t had a menstrual period for some time but informs the doctor that is normal for her. After consulting with her physician, the doctor tells Monica that she needs to cut back on her exercise routine and “put on some weight” in order to get pregnant. Monica is outraged because she figures she will gain enough weight when she is pregnant! Explain to Monica what has happened to her and why weight gain could help her achieve her goal of pregnancy.

41. The term “progesterone” means “for gestation (or pregnancy).” Describe how progesterone helps prepare the female body for pregnancy and helps maintain pregnancy.

42. After having borne five children, Mark’s wife Isabella insists that he have a vasectomy. Mark is afraid that he will “dry up” and won’t be able to perform sexually. How can you reassure him that his reproductive organs will function fine? Will Mark and Isabella be guaranteed that she will not become pregnant immediately after the vasectomy?

43. Would you expect the concentration of hypothalamic releasing and inhibiting hormones in a systemic venous blood sample to be higher, lower, or the same as the concentration of these hormones in a sample of hypothalamic–hypophyseal portal blood?

44. Thinking about the feedback control loop among TRH, TSH, and thyroid hormone, would you expect the concentration of TSH to be normal, above normal, or below normal in a person whose diet is deficient in iodine?

45. A patient displays symptoms of excess cortisol secretion. What factors could be measured in a blood sample to determine whether the condition is caused by a defect at the hypothalamus–anterior pituitary level or the adrenal cortex level?

46. A black market for growth hormone abuse exists among weight lifters and other athletes. What actions of growth hormone would induce a full-grown athlete to take supplemental doses of this hormone? What are the potential detrimental side eﬀects?

47. Diabetic patients who have surgery, become sick, or are under other physiological stress are told to monitor their blood sugar carefully because they may need to increase their insulin dose temporarily. What is the physiological explanation behind this advice?

48. One diagnostic test to determine the cause of hypercortisolism is a dexamethasone suppression test. Dexamethasone blocks secretion of ACTH by the pituitary. The following table shows the results from two patients given a dexamethasone suppression test. Can you tell from these results where the patients’ pathologies originate? Explain for each patient.

49. When blood test results came back last week, someone in the office spilled a cup of coﬀee on them, smearing the patient names and some of the numbers. One report shows elevated TSH levels, but the thyroid levels are so low they are unreadable. You have three charts waiting for test results on thyroid hormone levels. Your tentative diagnoses, based on physical findings and symptoms, for those three patients are: Mr. A: primary hypothyroidism Ms. B: primary hyperthyroidism Ms. C: secondary hyperthyroidism (a) Can you tell whose results are on the smeared report, based on the TSH results and the tentative diagnosis? (b) Can you rule out any of the three people based on those same criteria? Explain.

50. The following graph shows the results of a study done in Boston that compared blood vitamin D levels during summer and winter. Boston is located at 42 degrees north latitude, and weak sunlight in winter there does not allow skin synthesis of vitamin D. (a) Summarize the results shown in the graph. How many variables are shown in the graph that you must address in your summary? (b) Based on what you know, how could you explain the results of the study? (c) Would taking a multivitamin supplement aﬀect the results?