Childhood cancer survivors are at risk for neuroendocrine late effects. These effects are caused by radiation therapy to the brain in the area of the hypothalamus. The hypothalamus controls the way hormones are made by the pituitary gland. Radiation therapy may be given to treat cancer near the hypothalamus or as total-body irradiation (TBI) before a stem cell transplant.
Childhood cancer survivors who were treated with radiation to the brain may have low levels of any of the following pituitary hormones:
- Adrenocorticotropic hormone (controls the making of glucocorticoids).
- Growth hormone (helps promote growth and control metabolism).
- Prolactin (controls the making of breast milk).
- Thyroid-stimulating hormone (controls the making of thyroid hormones).
- Luteinizing hormone (controls reproduction).
- Follicle-stimulating hormone (controls reproduction).
Late effects that affect the hypothalamus may cause certain health problems.
Neuroendocrine late effects include the following:
- Adrenocorticotropin deficiency: A low level of adrenocorticotropic hormone is an uncommon late effect. It may occur after low doses of radiation therapy and rarely, after chemotherapy. Symptoms of adrenocorticotropin deficiency may not be severe and may not be noticed. Symptoms include weight loss for no known reason, not feeling hungry, nausea, vomiting, low blood pressure, and feeling tired.
- Growth hormone deficiency: A low level of growth hormone is the most common side effect of radiation to the brain in childhood cancer survivors. The higher the radiation dose and the longer the time since treatment, the greater the risk of this late effect. A low level of growth hormone in childhood results in adult height that is shorter than normal. Low growth hormone levels may be treated with growth hormone replacement therapy.
- Hyperprolactinemia: A high level of the hormone prolactin may occur after a high dose of radiation to the brain or surgery that affects part of the pituitary gland. A high level of prolactin may cause the following:
- Puberty at a later age than normal.
- Flow of breast milk in a woman who is not pregnant or breast-feeding.
- Less frequent or no menstrual periods or menstrual periods with a very light flow.
- Hot flashes (in women).
- Inability to become pregnant.
- Inability to have an erection needed for sexual intercourse.
- Lower sex drive (in men and women).
- Hypothyroidism: A low level of thyroid hormone may develop very slowly over time. Sometimes the symptoms of hypothyroidism are not noticed. Low thyroid hormone levels may cause slow growth and delayed puberty as well as other symptoms.
- Luteinizing hormone or follicle-stimulating hormone deficiency: Low levels of these hormones can cause different health problems. The type of problem depends on the radiation dose. A high dose of radiation may cause infertility. A low dose of radiation may cause puberty to occur at an earlier age than normal.