MEDS12003 Lecture 2: SS week 2 notes

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25 May 2018

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Week 2: Thyroid gland

Normal thyroid – Lt lobe

• paired right and let lobes

• Isthmus – midline

• Pyramidal lobe – 10-40%

• Each lobe <2cm in AP and TSV

• Isthmus 4-6cm

• Paired right and left lobes joined midline at

the isthmus.

• Pyramidal lobe only seen in some patients

and atrophies with age

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Sonographic features

• Size

o Lat lobe … 4 - 6 cm. L, 3 – 6 cm. W, 1.4

– 1.8 cm. AP

o Isthmus … 4 - 6 mm. AP

• Shape

o ovoid

• Echogenicity

o very homogenous, hyperechoic to

surrounding structures

• Contour

o smooth (capsule)

Thyroid gland arises from thyroid sac –diverticulum

which thickens in 3rd week of embryonic

development. Stalk between thyroid and tongue is

thyroglossal duct which opens in the embryo at the

Foramen cecum. Thyrogloassal duct atrophies by 6th

week, follicles form 8th week. Thyroglossal duct

normally closes after birth. Ectopic thyroid tissue

can be found anywhere along the descent from

Foramen cecum to the 1st tracheal ring.

Normal variants

• Agenesis

• Incomplete descent

• Pyramidal lobe –accessory lobe

• Incomplete isthmus

• Thyroglossal duct cyst

Physiology

• Endocrine gland -secretes hormones

o T3

o T4 –thyroxine

o Calcitonin

• Secretion controlled by TSH –pituitary gland

• Controls the basal metabolic rate (BMR)

o the amount of energy the body expends maintaining life

• Necessary for growth & development

T3 –Triiodothyronine, Thyroxine is the primary hormone of the thyroid. When thyroid hormone is needed,

TSH is secreted by the anterior pituitary gland which releases hormones into the bloodstream. Control of

TSH is regulated by thyrotropin-releasing factor produced in the hypothalamus. Decrease in BMR>low

thyroid hormone concentration>Increase in TRF causes inc in TSH and inc in thyroid hormones>restores

balance.

Figure 1Embryology

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Laboratory values

Thyroid scan

• What is expected from the thyroid scan?

o Screening

▪ Location of lesions, cystic vs solid

o Differentiate between:

▪ Generalised disease

▪ Multi-nodular disease

▪ Solitary lesions

o FNA guidance

Clinical indicators

• Abnormal thyroid hormone results (TSH, T4, T3)

• MNG (Multinodular Goitre)

• Lump in throat on swallowing

• Tightness in throat

• Follow up from previous imaging

Pathology

• Nodular Thyroid Disease

▪ Hyperplasia and Multi-Nodular Goitre

▪ Malignant thyroid disease

o Most common thyroid disease

o Thyroid cancer is rare → Thyroid Ca < 1% of all malignant neoplasms

o Most nodules are benign

• Diffuse Thyroid Disease

o Hashimoto’s Thyroiditis

o Graves’ Disease

70% of focal thyroid nodules are SOLID 4-7% of the adult population in the U.S. have palpable thyroid

nodules. Increased risk with exposure to ionizing radiation

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Document Summary

Isthmus midline: paired right and let lobes, pyramidal lobe 10-40, each lobe <2cm in ap and tsv, paired right and left lobes joined midline at. Isthmus 4-6cm the isthmus: pyramidal lobe only seen in some patients and atrophies with age. Sonographic features: size, lat lobe 4 - 6 cm. Ap: shape, ovoid, echogenicity, very homogenous, hyperechoic to surrounding structures, contour, smooth (capsule) Thyroid gland arises from thyroid sac diverticulum which thickens in 3rd week of embryonic development. Stalk between thyroid and tongue is thyroglossal duct which opens in the embryo at the. Thyrogloassal duct atrophies by 6th week, follicles form 8th week. Ectopic thyroid tissue can be found anywhere along the descent from. Incomplete descent: agenesis, pyramidal lobe accessory lobe, thyroglossal duct cyst. Physiology: endocrine gland -secretes hormones, t3, t4 thyroxine, calcitonin, secretion controlled by tsh pituitary gland, controls the basal metabolic rate (bmr) the amount of energy the body expends maintaining life, necessary for growth & development.

Related Questions

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 pressureâaltering 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. PWâs 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?

MEDS12003 Lecture 2: SS week 2 notes

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