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Late Effects of Treatment for Childhood Cancer (PDQ®): Treatment - Health Professional Information [NCI] - Late Effects of the Endocrine System

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Several investigations have demonstrated the superiority of ultrasound to clinical exam for detecting thyroid nodules/cancers and characterized ultrasonographic features of nodules that are more likely to be malignant.[15,16] However, primary screening for thyroid neoplasia (beyond physical exam with thyroid palpation) remains controversial because of the lack of data indicating a survival benefit and quality-of-life benefit associated with early detection and intervention. In fact, because these lesions tend to be indolent, are rarely life-threatening, and may clinically manifest many years after exposure to radiation, there are significant concerns regarding the costs and harms of overscreening.[17]

(Refer to the Subsequent Neoplasms section of this summary for information about subsequent thyroid cancers.)

Posttransplant thyroid dysfunction

Survivors of pediatric hematopoietic stem cell transplant are at increased risk of thyroid dysfunction, with the risk being much lower (15%-16%) after fractionated total-body irradiation (TBI), as opposed to single-dose TBI (46%-48%). Non-TBI-containing regimens historically were not associated with an increased risk. However, in a report from the Fred Hutchinson Cancer Research Center, the increased risk of thyroid dysfunction was not different between children receiving a TBI or busulfan-based regimen (P = .48).[18] Other high-dose therapies have not been studied. While mildly elevated TSH is common, it is usually accompanied by normal thyroxine concentration.[19,20]

Table 7. Thyroid Late Effects

Predisposing TherapyEndocrine/Metabolic EffectsHealth Screening
mIBG = metaiodobenzylguanidine; TSH = thyroid stimulating hormone.
Radiation impacting thyroid gland; thyroidectomyPrimary hypothyroidismTSH level
Radiation impacting thyroid glandHyperthyroidismFree thyroxine (Free T4) level
TSH level
Radiation impacting thyroid gland, including mIBGThyroid nodulesThyroid exam
Thyroid ultrasound

Central hypothyroidism is discussed with late effects that affect the pituitary gland.

Pituitary Gland

Survivors of childhood cancer are at risk for a spectrum of neuroendocrine abnormalities, primarily due to the effect of radiation therapy on the hypothalamus. Essentially all of the hypothalamic-pituitary axes are at risk.[21,22,23] The six anterior pituitary hormones and their major hypothalamic regulatory factors are outlined in Table 8.

Table 8. Anterior Pituitary Hormones and Major Hypothalamic Regulatory Factors

Pituitary HormoneHypothalamic FactorHypothalamic Regulation of the Pituitary Hormone
(-) = inhibitory; (+) = stimulatory.
Growth hormoneGrowth hormone-releasing hormone+
Somatostatin-
ProlactinDopamine-
Luteinizing hormoneGonadotropin-releasing hormone+
Follicle-stimulating hormoneGonadotropin-releasing hormone+
Thyroid-stimulating hormoneThyroid-releasing hormone+
Somatostatin-
AdrenocorticotropinCorticotropin-releasing hormone+
Vasopressin+

Growth hormone deficiency

Growth hormone deficiency (GHD) is the first and most common side effect of cranial irradiation in brain tumor survivors. The risk increases with radiation dose and time after treatment. GHD is the earliest hormone deficiency and is sensitive to low doses. Other hormone deficiencies require higher doses and their time to onset is much longer than for GHD.[24] The prevalence in pooled analysis was found to be approximately 35.6%.[25] The potential for neuroendocrine damage is likely to decrease because of the use of more focused radiation therapy and a decrease in dose for some malignancies such as medulloblastoma.

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WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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