A Prospective Study on Hypopituitarism after Radiotherapy in Non Pituitary Brain Tumors.
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Date
2016-07
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Abstract
Objective: Pituitary function and hypopituitarism have not been well evaluated in
adult patients with non-pituitary brain cancer.
Methods: Thirty-one (31) patients treated with primary or postoperative radiotherapy
(RT) for various cancers in the brain region without pre-existing hypothalamic pituitary
(HP) disorder from other causes were prospectively evaluated. Serum samples were
obtained from the patients to determine levels of growth hormone (GH), thyroidstimulating
hormone (TSH), and free thyroxine (FT4). Serum samples were measured
before treatment, 3 and 6 months after completion of radiation therapy (RT). The
hypothalamus-pituitary axis (HPA) and dose volume histograms (DVH) of the patients
were derived from their computed tomography-based treatment plans.
Results: Clinical hypopituitarism was not observed, but 83% of patients who tested for
hypopituitarism demonstrated subclinical hypopituitarism after a median interval of
6 months. Subclinical GH and TSH deficiency were observed in 17 (54%) and 9 (29%)
participants, respectively. Significant declines in TSH (p < 0.021), FT4 (p < 0.009),
and T4 (p < 0.036) levels after the RT course that can be interpreted as subclinical
central hypothyroidism were observed. Adjuvant chemotherapy and surgery did not
significantly influence the hypopituitarism (p = 0.698, p = 0.287, respectively). The
doses of radiation to the HPA region ranged from 241 to 5941 cGy (2.4-59.4 Gy).
The mean received dose (Dmean) and biological effective dose (BED) to the pituitary
were 36 and 59.6 Gy, respectively. Subclinical findings of late radiation effects were
observed in the HPA.
Conclusion: Radiation-induced hypopituitarism and central hypothyroidism are
regarded as primary damage to the pituitary gland. Time after therapy is critical and
so with time the incidence of growth hormone deficiency and thyroid stimulating
hormone deficiency is likely to significantly increase and to no longer be subclinical.
Neuronal cell death and degeneration because of the direct effects of radiation seem
to play basic roles.
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Keywords
Hypothalamus-pituitary axis, Hypopituitarism, Growth hormone, Thyroid-stimulating hormone, Hypothyroidism
Citation
Ordoni Jalal, Bakhshandeh Mohsen, Rakhsha Afshin, Azghandi Samira, Hajian Parastoo. A Prospective Study on Hypopituitarism after Radiotherapy in Non Pituitary Brain Tumors. Acta Medica International. 2016 Jul-Dec; 3(2): 72-77.