Category: Thyroid

Monitor: 8


Thursday, Apr 25
12:30 PM – 1:00 PM

Objective : To describe a case of hypothyroidism in a patient with congenital thyroid hemiagenesis and breast cancer treated with radiation.

Methods : Chart review.

Results : A 35-year-old female with locally recurrent right breast cancer presented with new hypothyroidism. The patient was on leuprolide and exemestane and had completed adjuvant chemotherapy with docetaxel and carboplatin 5 months prior to presentation. She was also treated with trastuzumab and pertuzumab, which were discontinued 3 months prior after repeat staining was negative for HER2. In addition to chemotherapy, the patient underwent adjuvant radiation to the right breast, axilla, infraclavicular and supraclavicular region completed 2 months prior to presentation. Thyroid function tests were ordered after the patient complained of fatigue, fluid retention, constipation, and weight gain, and were significant for a TSH of 132 (N: 0.3-4.7 mcIU/mL), undetectable FT4, and FT3 of 46 (N: 222-383 pg/dL). Tg and TPO antibodies were negative. TSH was normal 1 year prior. Thyroid ultrasound revealed a heterogeneous right lobe without discrete nodules and the left lobe was not visualized, suggestive of congenital thyroid hemiagenesis. On review of prior imaging, a radiation planning CT scan also showed thyroid hemiagenesis. She was initiated on thyroid hormone replacement therapy with levothyroxine and her thyroid function normalized 6 weeks later.

Discussion : The association between thyroid disease and breast cancer is an area of ongoing investigation. One study shows a significant increase in self-reported hypothyroidism in breast cancer patients who have undergone multimodal therapy, however the data are not consistent. Case series suggest a significant relationship between radiation therapy and hypothyroidism, though the time to onset is often more prolonged than seen in our patient. Smaller thyroid volumes, as seen in this case with thyroid hemiagenesis, may predict an increased risk of radiation-associated hypothyroidism. Specific to our patient, the CT scan done for radiation planning did show thyroid hemiagensis, however this was not detailed in the initial report. While thyroid hemiagenesis is rare with a reported prevalence between 0.05%-0.5% of the population, it may be reasonable to review existing imaging prior to radiation to assess if post-radiation thyroid function screening is necessary. Notably, while there may also be an association between anti-HER2 therapy and autoimmune thyroid disease, this patient’s autoimmune thyroid disease markers were negative.

Conclusion : In this patient with congenital left thyroid hemiagenesis it is important to consider the increased risk of hypothyroidism after radiation therapy for breast cancer.


Anna Betlachin

Internal Medicine Resident
University of California, Los Angeles

Dr. Anna Betlachin is an Internal Medicine Resident at the University of California, Los Angeles. She will be starting her endocrinology fellowship at UCLA in 2019.

Shira Grock

Clinical Instructor
University of California, Los Angeles

Dr. Shira Grock was born and raised in Los Angeles and received her undergraduate degree from UC Berkeley. She then earned her medical degree from University of Southern California where she was elected for Alpha Omega Alpha Honor Society. She went on to complete her Internal Medicine training at Mount Sinai Hospital in New York City and returned to Los Angeles for her endocrinology fellowship at UCLA. Dr. Grock then joined faculty at UCLA and practices general endocrinology in Santa Monica.

Stephanie Smooke-Praw

Associate Professor
University of California, Los Angeles

Dr. Stephanie Smooke-Praw is an Associate Professor of Medicine at the UCLA David Geffen School of Medicine and clinical endocrinologist.

After pursuing undergraduate studies at Yale University and a masters degree at the University of London, Dr. Smooke-Praw completed medical school at the UCLA David Geffen School of Medicine followed by internal medicine training at UCLA Hospital. Following residency, she served as Chief Resident for the Department of Internal Medicine before completing endocrine fellowship at UCLA.

Dr. Smooke-Praw has clinical and research interests in thyroid disorders (including over and underactive thyroid conditions and thyroid nodules) and thyroid cancer. She also sees patients with parathyroid disease and PCOS, among other endocrine disorders. She lectures frequently on thyroid disease and has published in the field of thyroid cancer.