Hypothyroidism After a Cancer Diagnosis: Etiology, Diagnosis, Complications, and Management

Abstract

Hypothyroidism is a common disease that is easily treated in the majority of cases, when readily diagnosed; however, presentation of an aggregate of its symptoms is often clinically overlooked or attributed to another disease and can potentially be lethal. Already prevalent in older women, its occurrence in younger patients is rising as a result of radiation therapy, radioactive iodine therapy, and newer antineoplastic agents used to manage various malignancies. The presence of nonspecific constitutional symptoms and neuropsychiatric complaints in cancer patients can be attributed to a myriad of other diagnoses and therapies. Thyroid dysfunction can be easily overlooked in cancer patients because of the complexity of cancer's clinical picture, particularly in the pediatric population. Underdiagnosis can have important consequences for the management of both hypothyroidism and the malignancy. At minimum, quality of life is adversely affected. Untreated hypothyroidism can lead to heart failure, psychosis, and coma and can reduce the effectiveness of potentially life-saving cancer therapies, whereas iatrogenic causes can provoke atrial fibrillation and osteoporosis. Consequently, the diagnosis and treatment of hypothyroidism in cancer patients are pertinent. We summarize the history, epidemiology, pathophysiology, clinical diagnosis, and management of hypothyroidism in cancer patients. The Oncologist 2014;19:34-43Implications for Practice: Clinicians should be aware of the role that hypothyroidism can play in the diagnosis, treatment, and recovery of cancer. Because the myriad of symptoms associated with hypothyroidism can easily be attributed to the initial malignancy, to chemotherapy or radiation therapy, or to cancer recurrence, it is easy to miss the diagnosis of hypothyroidism. Timely diagnosis and treatment is necessary to minimize the complications of hypothyroidism, to optimize cancer therapy, and to minimize recurrence.We highlight newer therapies associated with hypothyroidism and the negative impact that hypothyroidism can have in patients with a malignancy.

Hormonal dysfunction is frequent in cancer survivors treated with radiotherapy to the head and neck region

“…Moreover, newer agents used in cancer treatment, such as tyrosine kinase inhibitors and vascular endothelial growth factor receptor blockers, have also been reported to cause hypothyroidism in a substantial proportion of patients [21,22]. Conversely, traditional chemotherapy, such as the substances used in this study, rarely causes thyroid dysfunction in the absence of radiation [22], though the question of whether chemotherapy sensitizes the thyroid gland to the harmful effects of radiotherapy is controversial [11,23].…”

“…The growth hormone (GH) axis is considered the most radiosensitive hormone axis. Subnormal GH values after stimulation have been described after radiation doses of [18][19][20][21][22][23][24] Gy to the pituitary gland [14,16], whereas dysfunction in the HP-gonadal axis is rare in cancer survivors who received doses below 40 Gy to the pituitary gland [16]. The HP-thyroid and HP-adrenal axes are even more radioresistant, but hormonal dysfunction in these axes has been described as frequent after higher doses (≥50 Gy) to the pituitary gland [14,16].…”

Outpatient Endocrine Diagnosis and Treatment of Thyroid Diseases and Disorders in a Portuguese Public University Hospital

“…That although treatment is deemed easy it seems rather far from perfect is evident since even with specialist care almost a quarter presented thyroid dysfunction, either subclinical or clinical hypothyroidism or hyperthyroidism and these rates are not very different regarding the first appointment. Treatment of hypothyroidism is far from perfect even if it is easy, since many factors affect the daily dose needed, many drug interactions are recognized and non-adherence even self-reported is great, even if we do not consider ongoing controversies regarding the advantages of also replacing T3 [42]. One study showed that regarding patients being treated with levothyroxine, 18% had increased TSH levels and 22% decreased TSH levels, with rates not very different from those found in the present report [43].…”

Onset of hypothyroidism after total laryngectomy: Effects of thyroid gland surgery and preoperative and postoperative radiotherapy

“…Hypothyroidism is an irreversible condition, requiring lifelong thyroid hormone substitution. It is essential to recognize and treat the symptoms of hypothyroidism in an early stage especially because effective treatment is available . Previous studies on hypothyroidism as a consequence of radiotherapy or (hemi)thyroidectomy in the treatment of laryngeal or hypopharyngeal cancer, were performed before the introduction of intensity‐modulated radiotherapy or did not evaluate the impact of various combined treatment strategies used nowadays …”