Hazel C. a 30-year-old female demonstrated a subtle onset of the following sympt
ID: 80096 • Letter: H
Question
Hazel C. a 30-year-old female demonstrated a subtle onset of the following symptoms: dull facial expression; droopy eyelids; puffiness of the face and periorbital swelling; sparse, dry hair; dry, scaly skin; evidence of intellectual impairment; lethargy; a change of personality; bradycardia (60 b/min); a blood pressure of 90/70; constipation, and hypothermia. Plasma concentrations of total and free T4 and T3 follow:
T4
T3
Total
3 ug/dL (normal = 4-12 ug/dL)
0.14 ng/dL (normal = 75-195 ng/dL)
Free
0.6 ng/dL
0.01 ng/dL
Radioimmunoassay (RIA) (Links to an external site.)Links to an external site. of peripheral blood indicated elevated TSH levels. A TSH stimulation test did not increase the output of thyroid hormones from the thyroid gland.
1. Why does Hazel have a lower-than-normal body temperature?
2. Describe the feedback loop involved.
3. What is the most likely diagnosis for Hazel?
4. Would you expect to find a palpable goiter? Explain your answer.
5. What is the most likely explanation for the bradycardia and low blood pressure? Constipation?
6. Describe a suitable treatment for Hazel. Would this treatment require injections or capsules?
7. Is this treatment expected to return blood pressure and heart rate to normal? Why or why not?
T4
T3
Total
3 ug/dL (normal = 4-12 ug/dL)
0.14 ng/dL (normal = 75-195 ng/dL)
Free
0.6 ng/dL
0.01 ng/dL
Explanation / Answer
1) Hazel has low levels of thyroid hormones in her blood. Thyroid hormones are essential for maintaining basal metabolic rate (BMR), heart rate and blood pressure. Because of decrease in basal metabolic rate, hazel has lower than normal body temperature.
2) Negative feeedback loop is involved in control of thyroid hormone secretion. Throtropin releasing hormone (TRH) is secreted by hypothalamus acts on pituitary to release thyroid stimulating hormone (TSH). TSH secreted by the pituitary stimulates thyroid gland to release the thyroid hormones thyroxine (T4) and triiodothyronine (T3). When the levels of T4 and T3 in blood increases it exerts negative feedback inhibition of both TRH and TSH.
3) The most likely diagnosis for Hazel is hypothyroidism due to iodine deficiency.
4) Palpable goitre could be found. It occurs due to hyperplasia of the thyroid gland to compensate for the decreased efficacy.
5) Thyroid hormones are essential for maintaining adrenergic receptor complex and its signal system, the GTP/Adenyl cyclase/Cyclic AMP units in the cell membrane. Lower levels of thyroid hormones will result in malfunctioning of adrenergic system causing bradycardia, low blood pressure and constipation.
6) Treatment is Iodine supplementation. Iodine can be taken orally.
7) Iodine supplementation will increase the secretion of thyroid hormones. Gradually the symptoms of hypothyroidism will disappear. Blood pressure and heart rate will return to normal levels.
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