EXERCISE 4: Endocrine System Physiology Activity 1: Metabolism and Thyroid Hormone Normal rat

Thyroidectomized rat

Hypophysectomized rat

Weight (g)

Variable, 249–251

Variable, 244–246

Variable, 244–246

ml O2 used in 1 minute

Variable, 7.0–7.2

Variable, 6.2–6.4

Variable, 6.2–6.4

ml O2 used per hour

420–432*

372–384*

372–384*

Metabolic rate

1673–1735 ml O2/kg/hr*

1512–1574 ml O2/kg/hr*

1512–1574 ml O2/kg/hr*

Palpation results

No mass

No mass

No mass

Weight (g)

Same as baseline

Same as baseline

Same as baseline

ml O2 used in 1 minute

Variable, 8.3–8.5

Variable, 7.7–7.9

Variable, 7.7–7.9

ml O2 used per hour

498–510 ml

462–474 ml

462–474 ml

Metabolic rate

1984–2048 ml O2/kg/hr

1878–1943 ml O2/kg/hr

1878–1943 ml O2/kg/hr

Palpation results

No mass

No mass

No mass

Weight (g)

Same as baseline

Same as baseline

Same as baseline

ml O2 used in 1 minute

Variable, 7.9–8.1

Variable, 6.2–6.4

Variable, 7.7–7.9

ml O2 used per hour

474–486 ml ml O2/kg/hr

372–384 ml

462–474 ml

Metabolic rate

1904 ml O2/kg/hr

1512–1574 ml O2/kg/hr

1878–1943 ml O2/kg/hr

Palpation results

1904 ml O2/kg/hr Mass

No mass

Mass

Baseline

With thyroxine

With TSH

With propylthiouracil

Weight (g)

Same as baseline

Same as baseline

Same as baseline

ml O2 used in 1 minute

Variable, 6.2–6.4

Variable, 6.2–6.4

Variable, 6.2–6.4

ml O2 used per hour

372–384 ml

372–384 ml

372–384 ml

Metabolic rate

1482–1542 ml O2/kg/hr

1512–1574 ml O2/kg/hr

1512–1574 ml O2/kg/hr

Palpation results

Mass

No mass

No mass

* Data populated by student calculations.

Part 1 1. Which rat had the fastest basal metabolic rate (BMR)? The normal rat had the fastest basal metabolic rate because it was not missing its pituitary gland or its thyroid gland. 2. Why did the metabolic rates differ between the normal rat and the surgically altered rats? How well did the results compare with your prediction? The normal rat has the highest BMR because it has the glands required to stimulate and regulate the release of thyroid hormones. 3. If an animal has been thyroidectomized, what hormone(s) would be missing in its blood? For the thyroidectomized rats the hormones missing will be triiodothyronine and thyroxine. 4. If an animal has been hypophysectomized, what effect would you expect to see in the hormone levels in its body? For the hypophysectomized rat, the TSH will be missing due to the missing pituitary gland. Part 2 5. What was the effect of thyroxine injections on the normal rat’s BMR? The levels were a little off. The normal rat was hyperthyroidic because the thyroxine increases the metabolic rate but it did not develop goiter. 6. What was the effect of thyroxine injections on the thyroidectomized rat’s BMR? How does the BMR in this case compare with the normal rat’s BMR? Was the dose of thyroxine in the syringe too large, too small, or just right? The BMR increased for the thyroidectomized rat with thyroxine injections. The BMR was still a little bit below the normal rat’s BMR with thyroxine. The dose was too low. 7. What was the effect of thyroxine injections on the hypophysectomized rat’s BMR? How does the BMR in this case compare with the normal rat’s BMR? Was the dose of thyroxine in the syringe too large, too small, or just right? The BMR increased for the hypophysectomized rat with thyroxine injections. The BMR was still a little bit below the normal rat’s BMR with thyroxine. The dose was too low. Part 3 8. What was the effect of thyroid-stimulating hormone (TSH) injections on the normal rat’s BMR? The effect of TSH was to increase the normal rat’s BMR. 9. What was the effect of TSH injections on the thyroidectomized rat’s BMR? How does the BMR in this case

compare with the normal rat’s BMR? Why was this effect observed? There was no effect on the thyroidectomized rat’s BMR with the injection of TSH because there was no thyroid gland to stimulate. 10. What was the effect of TSH injections on the hypophysectomized rat’s BMR? How does the BMR in this case compare with the normal rat’s BMR? Was the dose of TSH in the syringe too large, too small, or just right? The hypophysectomized rat BMR increased with TSH. The BMR was just below the normal rat but still lower. the syringe amount was a little too low. Part 4 11. What was the effect of propylthiouracil (PTU) injections on the normal rat’s BMR? Why did this rat develop a palpable goiter? The effect of PTU injections on the normal rat was to decrease the BMR. The palpable goiter was due to the buildup of the precursors to thyroxine. 12. What was the effect of PTU injections on the thyroidectomized rat’s BMR? How does the BMR in this case compare with the normal rat’s BMR? Why was this effect observed? The effect of PTU injections on the thyroidectomized rat was not visible because there was no thyroid gland to be affected. 13. What was the effect of PTU injections on the hypophysectomized rat’s BMR? How does the BMR in this case compare with the normal rat’s BMR? Why was this effect observed? The effect of PTU injections on the hypophysectomized rat was not visible because the rat is missing the pituitary gland.

Activity 2: Plasma Glucose, Insulin, and Diabetes Mellitus (pp. 64–67) Chart 2.1 Glucose Standard Curve Results Tube

Optical density

Glucose (mg/dl)

1

0.30

30

2

0.50

60

3

0.60

90

4

0.80

120

5

1.00

150

Chart 2.2 Fasting Plasma Glucose Results Sample

Optical density

Glucose (mg/dl)

1

0.73

104

2

0.79

115

3

0.89

131

4

0.83

122

5

0.96

143

1.What is a glucose standard curve, and why did you need to obtain one for this experiment? Did you correctly predict how you would measure the amount of plasma glucose in a patient sample using the glucose standard curve? The glucose standard curve correlates the intensity of the color obtained and measured on a spectrophotometer (optical density) to the glucose concentration. 2. Which patient(s) had glucose reading(s) in the diabetic range? Can you say with certainty whether each of these patients has type 1 or type 2 diabetes? Why or why not? Patients 3 and 5 had a fasting plasma glucose in the diabetic range. It is not possible to tell if they have type 1 or type 2 just from their fasting plasma glucose. 3. Describe the diagnosis for patient 3, who was also pregnant at the time of this assay. This would be described as gestational diabetes. The diabetes often disappears after the pregnancy. 4. Which patient(s) had normal glucose reading(s)? Patients 1 and 2 were in the normal range. 5. What are some lifestyle choices these patients with normal plasma glucose readings might recommend to the borderline impaired patients? Limit the ingestion of simple sugars. Choose “good” carbohydrates such as whole wheat and fiber based carbohydrate choices.

Activity 3: Hormone Replacement Therapy Rat

T score

Contro

Variable, –2.81 to –2.85

Estrogen

Variable, –1.52 to –1.74

Calcitonin

Variable, –2.05 to –2.35

1. Why were ovariectomized rats used in this experiment? How does the fact that the rats are ovariectomized explain their baseline T scores? The ovaries produce estrogen and estrogen stimulates bone growth. Without estrogen bone growth is impaired and osteoporosis is a common result. 2. What effect did the administration of saline injections have on the control rat? How well did the results compare with your prediction? The saline had no effect. The inclusion of the saline as a negative control is to insure that saline has no effect. 3. What effect did the administration of estrogen injections have on the estrogen-treated rat? How well did the results compare with your prediction? The estrogen injections did increase the rat’s vertebral bone density as predicted and as indicated by the negative T score. 4. What effect did the administration of calcitonin injections have on the calcitonin-treated rat? How well did the results compare with your prediction? The calcitonin showed no change in the vertebral bone density. This is somewhat contradictory to what is expected. We do not know why. 5. What are some health risks that postmenopausal women must consider when contemplating estrogen hormone replacement therapy? Health risks of estrogen therapy include an increased incidence of uterine cancer, breast cancer and blood clots.

Activity 4: Measuring Cortisol and Adrenocorticotropic Hormone Patient

Cortisol (mcg/dl)

Cortisol level

ACTH (pg/ml)

ACTH level

1

Variable, 3±1

Low*

Variable, 18±2

Low*

2

Variable, 35±5

High*

Variable, 13±2

Low*

3

Variable, 45±5

High*

Variable, 86±5

High*

4

Variable, 3±1

Low*

Variable, 100±5

High*

5

Variable, 50±5

High*

Variable, 18±2

Low*

* The entries in these columns are designated by the student in the software.

1. Which patient would most likely be diagnosed with Cushing’s disease? Why? Patient 3 would be diagnosed with Cushing’s disease because the levels of cortisol and ACTH are both high. 2. Which two patients have hormone levels characteristic of Cushing’s syndrome? Patients 2 and 5 both have high levels of cortisol and low ACTH. These levels are characteristic of Cushing’s syndrome. 3. Patient 2 is being treated for rheumatoid arthritis with prednisone. How does this information change the diagnosis? The diagnosis would change to iatrogenic or physician-induced Cushing’s syndrome. 4. Which patient would most likely be diagnosed with Addison’s disease? Why? Patient 4 would be diagnosed with Addison’s disease because the level of ACTH is high but the level of cortisol is low.