Endocrine System Physiology

The following questions refer to Activity 1: Determining Baseline Metabolic Rates. 1. Which rat had the fastest baseline metabolic rate?
The normal rat had the fastest baseline metabolic rate.

2. Compare the baseline metabolic rates for the thyroidectomized rat and the normal rat and explain your results.
The normal rat’s baseline metabolic rate was faster than that of the thyroidectomized rat’s baseline metabolic rate. 3. Compare the baseline metabolic rates for the hypophysectomized rat and the normal rat and explain your results. The normal rat’s baseline metabolic rates were faster than that of the hypophysectomized rat’s baseline metabolic rate because it lacked thyroid-stimulating hormones. The following questions refer to Activity 2: Determining the Effect of Thyroxine on Metabolic Rate. 4. What effect did administering thyroxine have on each of the rats?

It caused the metabolic rate to increase in all three rats.

5. Explain why thyroxine had these effects.
It is a thyroid-stimulating hormone that causes more metabolism to occur.

The following questions refer to Activity 3: Determining the Effect of TSH on Metabolic Rate. 6. Was there a change in the metabolic rate of the thyroidectomized rat with the administration of TSH? Explain your results. There was no change in the metabolic rate. It stayed the same as the baseline metabolic rate.

7. Did the results for the thyroidectomized rat indicate hyperthyroidism or hypothyroidism? It indicated hypothyroidism since there is no longer any thyroid.

The following questions refer to Activity 4: Determining the Effect of Propylthiouracil on Metabolic Rate. 8. Describe the effect of administering propylthiouracil on each of the rats, and explain why it had this effect. It decreased the baseline metabolic rate in the normal and hypophysectomized rats. Propylthiouracil blocks the attachment of iodine to tyrosine residues and interferes with the conversion of thyroxine to triiodothyronine, therefore, causing the baseline metabolic rate to decrease.

9. Do you think the drug propylthiouracil is used to treat hypothyroidism or hyperthyroidism? Explain your answer. It is used to treat hyperthyroidism because propylthiauracil reduces or decreases the effects of thyroxine.

Hormone Replacement Therapy
The following questions refer to Activity 5: Hormone Replacement Therapy. 10. Explain why ovariectomized rats were used in this experiment and correlate this to their baseline T score. Ovariectomized rats were used in this experiment because they have had their ovaries removed, therefore, there is no estrogen being produced anymore. Their baseline T score is -2.6 because osteoporosis is apparent.

11. Recap your predictions regarding the effects of calcitonin and estrogen on bone density and explain why you made those predictions. I predicted that their bone density would improve with the injections of calcitonin and estrogen because they are hormone replacement therapies. Calcitonin would help with the production of osteoclasts and estrogen would help increase the bone density.

12. Why was one of the ovariectomized rats injected with saline? One of the rats was injected with saline, which is just water and salt, to be the controlled variable in the experiment. With saline, no affects would take place.

13. What effect did the administration of estrogen injections have on the estrogen-treated rat? It increased bone density that resulted in osteopenia.
14. What effect did the administration of calcitonin injections have on the calcitonin-treated rat? It increased bone density that changed from osteoporosis to osteopenia. 15. How did your results compare to your predictions?

My predictions were accurate that the injections would help increase bone density.

Insulin and Diabetes
The following question refers to Activity 6: Obtaining a Glucose Standard Curve.

16. What is a glucose standard curve, and how can you use this tool to determine a concentration of glucose? The glucose standard curve helps gives a reference for converting optical density readings. You can use this to help determine how much glucose is present in someone’s blood sample.

The following questions refer to Activity 7: Measuring Fasting Plasma Glucose. 17. Which patient(s) had glucose reading(s) in the normal range?
Patient #1
18. Which patient(s) had glucose reading(s) in the diabetic range?
Patients #3 and #5

19. Which patient(s) had glucose reading(s) in the impaired range?
Patients #2 and #4
20. Describe the diagnosis for Patient 3.
The diagnosis for patient #3 was Gestational Diabetes.
The following questions refer to Activity 8: Measuring Cortisol and Adrenocorticotropic Hormone. 21. Which patient would most likely be diagnosed with Cushing’s disease? Why?
Patient #3 would most likely be diagnosed with Cushing’s disease because there were high levels of cortisol and ACTH in this patient.

22. Which two patients have hormone levels characteristic of Cushing’s syndrome?  Patients #2 and #5