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Why does thyroid gland enlarge both in hypothyroidismand hyperthyroidism?
Hypothyroid goitre is due to lack of iodine in diet andhyperthyroid goitre (Exopthalmic goitre, Grave's disease) is due tooversecretion of thyroxine, or Thyroid stimulating Hormone. Howdoes these two apparently opposite effects produce similar physicalmanifestation of the disorder (symptom) i.e is the enlargement ofthe thyroid gland?

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Reid Wolff
Reid WolffLv2
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Medical History:
Ms. PW, a 58 yr old Caucasian woman, is referred by her physician for the development of an exercise prescription. She is 6 yr postmenopausal and has never been on hormone replacement therapy. In 1987, she was diagnosed with hyperthyroidism (overactive thyroid gland), which was treated with radioactive iodine. Since the treatment, Ms. PW has been on synthroid, a drug used when the thyroid gland does not produce enough thyroid hormones. She has mild hypertension, which is regulated by blood pressure–altering medications. Ms. PW is 5 ft 5 in. (165 cm) tall with a weight of 128 lb (58 kg), and her body mass index is in the normal range. She does not follow a regular exercise regimen but reports that she enjoys biking.

Diagnosis:
A few months ago, Ms. PW was diagnosed with osteopenia. Considering her medical history, she is likely to become osteoporotic. Her risk factors are age, sedentary lifestyle, being Caucasian, being petite in stature, loss of menstrual function, and lack of thyroid hormone production.

Exercise Test Results:
She recently underwent an exercise stress test that was normal, but no physiological testing was done other than regular blood chemistries.

Exercise Prescription:
A walking program is surely the best choice because it has the potential of improving not only her cardiorespiratory fitness, but also her bone density. However, Ms. PW is particularly fond of bicycling, and therefore the exercise prescription will incorporate some biking activities, as that is likely to increase her adherence to exercise. These cardiorespiratory activities will start slow and gradually progress over time. Ultimately, her goal would be to walk (3.5 mph [5.6 kph] or faster) or bike 30 to 45 min five times a week. In order to reach this goal, Ms. PW may need to start walking or biking at a slower pace and for a shorter distance, but she should strive to exercise five times a week. After it is determined that she can comfortably handle the speed and distance used for the first 2 wk, these two components should be gradually increased. The best choice is to increase the speed a couple of days a week and increase the distance covered on the other days of the week.
A resistance training program should also be implemented, and may be more beneficial with respect to bone than the cardiorespiratory program. Resistance training should also start slowly, with the frequency beginning at 2 d/wk and moving up to 3 or 4 d/wk. Initially, resistance should be low enough that she can easily complete 12 repetitions of an exercise without undue strain. Exercises that target all the major muscle groups should be incorporated, especially for the legs and back. However, exercises that involve spinal flexion should be avoided. In order to strengthen abdominal muscles, Ms. PW can do leg lifts or modified sit-ups, in which only the head is being lifted off the floor. Upon completion of the first 2 wk, during which the patient does one set of 12 repetitions of each exercise, she can add a second set. This same progression can be used after Ms. PW completes another 2 wk. At this point, the patient should start increasing the intensity by slowly increasing the resistance. An adequate resistance at this point would allow the patient to complete no more than 10 repetitions on the second set. All exercises should be performed with slow, controlled movements. Based on Ms. PW’s medical history, this exercise prescription should be well tolerated and should provide optimal health benefits. Individual cases vary, however, and for a woman who has suffered fragility fractures as a result of osteoporosis, even the minimal exercise described here may not be tolerated initially. Such a patient will need a more gradual, less intense program.

Questions:
1. What other information should be obtained from Ms. PW?

2. What other physiological tests might be recommended?

3. Explain the difference in benefits achieved through cardiorespiratory training versus resistance training for this patient. Why is it always important to incorporate both?

1). Thyroid hormone (TH) has been identified as one of the factors promoting phenotype development in the Mexican axolotl salamander. Which of the following statements regarding the impact of TH is FALSE?

A). Axolotls maturing in water with high concentration of TH (thyroxine; T4) metamorphose into a terrestrial form.

B). A genome-wide scan of both the axolotl and its sister species found a large reduction in the number of mRNA transcripts that regulate the production of TH.

C). Adding TH (thyroxine; T4) to the water in which axolotl individuals are reared causes them to remain in a larval stage.

D). Most salamander species produce a burst of TH when they move from water to land.

2).What would be an appropriate evolutionary explanation of the fact that the ordering of some homeotic genes (such as Hox genes) on vertebrate chromosomes parallels the ordering of homeotic genes on fruit fly chromosomes?

A). The similarity is a coincidence, not documented in other invertebrates and largely a result of random mutations.

B). Homeotic genes show that insects and vertebrates are closer relatives than the traditional classification system indicates.

C). Homeotic genes of different animal lineages might be ordered in a similar fashion, yet their sequences are completely different.

D). The similar ordering of homeotic genes in animals, both vertebrate and insect, is due to ancient homology.

3). Which of the following correctly defines "homeotic genes"?

A). Homeotic genes encode proteins that control the cellular environment in a differentiated cell tissue.

B). Homeotic genes are DNA sequences that turn off, but not on, the expression of other genes and are controlled by "master-switch" genes.

C). Homeotic genes are "master-switch" genes that control other genes in a set sequence and thereby affect cell size, shape, division, and the positioning of the cells within the organism.

D). Homeotic genes are DNA sequences that turn on, but not off, the expression of other genes and are controlled by "master-switch" genes.

4). Which of the following is NOT considered a type of heterochrony (change in the rate and timing of development)?

A). hypermorphosis

B). acceleration

C). neoteny

D). ontogeny

5). How does the dominance theory explain why the heterogametic sex is at a disadvantage in Haldane's rule?

A). Beneficial dominant alleles will never be fully expressed in hybrids as they only carry one copy of the sex chromosome that carries the allele.

B). If a dominant allele has a negative effect on the fitness of hybrids, it will always be expressed in the heterogametic hybrids that possess that allele because they only need one copy of the respective sex chromosome.

C). If a recessive allele linked to a sex chromosome has a negative effect on the fitness of hybrids, that allele will always be expressed in the heterogametic hybrids that possess that allele because they only have one copy of the sex chromosome that carries the allele.

D). If a recessive allele linked to a sex chromosome has a positive effect on the fitness of hybrids, that allele will never be expressed in the heterogametic hybrids that possess that allele because they only have one copy of the sex chromosome that carries the allele.

6). In a hypothetical flowering plant species, one population evolves a different response to environmental stimuli and begins to bloom significantly later in the season than nearby populations. What type of reproductive isolating mechanism would this be?

A). hybrid sterility

B). postzygotic

C). prezygotic

D). gametic incompatibility

7). In a study of red spruce trees and black spruce trees, scientists found that the red spruce was living in a smaller geographic area and had much less genetic variation than the black spruce. They proposed that the red spruce might have arisen from a southern population of black spruce, which became geographically isolated from other black spruce populations at some point during the Pleistocene glaciations. What is this an example of?

A). allopatric speciation with the vicariance model

B). sympatric speciation

C). allopatric speciation with the peripheral isolate model

D). sympatric speciation with the ring species model

8). Which of the following defines Haldane's rule and its predictions?

A). If among hybrid offspring one sex is absent, rare, or sterile, that sex is always male.

B). If among hybrid offspring one sex is absent, rare, or sterile, that sex is always female.

C). If among hybrid offspring one sex is absent, rare, or sterile, that sex is heterogametic (has two different sex chromosomes).

D). If among hybrid offspring one sex is absent, rare, or sterile, that sex is homogametic (has two of the same sex chromosomes).

8.) Which of the following statements best explains secondary reinforcement?

A). If the reproductive isolating mechanisms that developed during the geographic isolation are strong but the hybrids have higher fitness than the parent species, then the speciation process will cease.

B). If the reproductive isolating mechanisms that developed during the geographic isolation are somewhat weak but the hybrids between two populations have lower fitness, then the speciation process may continue.

C). If the reproductive isolating mechanisms that developed during the geographic isolation are sufficiently weak as to allow free interbreeding across reunited populations, then the speciation process will halt and a single species will remain.

D). When geographic isolation comes to an end, two populations always complete the divergence process and become separate species.

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