Early effects of cranial irradiation on hypothalamic pituitary function

Area of Science:

• Endocrinology
• Oncology
• Radiation Oncology

Background:

• Nasopharyngeal carcinoma treatment often involves cranial irradiation.
• The hypothalamus-pituitary axis is sensitive to radiation and chemotherapy.
• Long-term endocrine function after treatment requires thorough investigation.

Purpose of the Study:

• To assess hypothalamic-pituitary function six months after cranial irradiation for nasopharyngeal carcinoma.
• To evaluate the impact of radiosensitizing chemotherapy on endocrine function.
• To identify early signs of endocrine dysfunction post-treatment.

Main Methods:

• Study included 25 nasopharyngeal carcinoma patients before and 6 months after cranial irradiation.
• Hormonal levels and responses to releasing hormones (TRH, LHRH, CRH, GRH) were measured.
• Insulin tolerance test (ITT) was performed to assess growth hormone (GH) and adrenocorticotropic hormone (ACTH) responses.

Main Results:

• Significant increases in baseline serum thyrotropin (TSH) and follicle-stimulating hormone (FSH) were observed.
• TSH response to TRH increased, with delayed peaks in 21 patients, suggesting primary hypothyroidism and TRH release defects.
• Altered FSH and luteinizing hormone (LH) responses to LHRH noted in males, with chemotherapy modifying the response pattern.
• Adrenocorticotropic hormone (ACTH) response to CRH unchanged, but integrated cortisol response increased.
• Growth hormone (GH) response to GRH unchanged, but increased response to ITT observed.

Conclusions:

• Cranial irradiation significantly impairs hypothalamic-pituitary endocrine axes six months post-treatment.
• Both hypothyroidism and altered gonadotropin function are early consequences.
• Radiosensitizing chemotherapy may modulate the extent of pituitary hormone response changes.