Thyroid cancer is the most common endocrine malignancy accounting for 90% of all endocrine cancers. It constitutes less than 1% of all malignant tumors.(1) Annual incidence of thyroid cancer varies from 0.5 to 10 per 100000 population throughout the world.(1) Age and gender adjusted incidence of thyroid cancer has increased than any other malignancy. According to Surveillance, Epidemiology and End Result Programme (SEER) 60,220 new cases are found in USA in 2013, the number of cases was 22,348 in 2002.(2) The rate of thyroid cancer among the reproductive age group is significant (59.6% among the age limit of 20-54 years).(2) The prognosis of differentiated thyroid cancer (DTC) if appropriately treated is very good in both nonmetastatic and local or distant metastatic cases.(3) In USA an estimated 190,000 survivors of thyroid carcinoma found, some for more than 40 years.(1) Treatment of DTC is radioactive iodine (RAI) (I-131) therapy for ablation of thyroid remnant after total thyroidectomy and recurrence and/or metastases. RAI therapy is usually performed 15-40 days after total thyroidectomy and can be repeated at 6 months interval. The dose of RAI ranges from 1.1 to 5.5 GBq (30 to 150 mCi) or more. (4) Since young adults in their reproductive age can be affected by thyroid cancer and have excellent prognosis after treatment, these group may be exposed to large dose of I-131 in their course of disease.(3) Longer survival of the cancer patients gives rise to questions about the quality of survival and complications of cancer therapy. Therefore question arises about the effect of RAI therapy on the fertility of young patients.(5) Gonadal damage following chemotherapy and radiotherapy is well established. (5) After oral administration of I-131, it goes to the site of thyroid follicular cells – healthy or cancerous and excess RAI is cleared from the body through kidneys and gut. Therefore, blood, urinary bladder, gut and pelvic metastasis act as primary sources of radiation to male and female gonads. Furthermore, patients are hypothyroid at the time of RAI therapy which causes slow gut and renal clearance of radioiodine prolonging gonadal exposure to radiation.(6) Germinal cell damage following RAI therapy for DTC in a small group of male patients has been reported . (7) Similarly, transient ovarian failure and increase incidence of miscarriage has also been reported within one year of RAI therapy. (8) A systemic review reported:
Abnormalities in testicular function are common within several months of a single therapeutic dose of RAI. Biochemical abnormalities usually resolves within 18 months after therapy. The risk of persistent gonadal dysfunction increases with repeated RAI therapy. (9)
RAI therapy is routinely practiced in National Institute of Nuclear Medicine & Allied Sciences (NINMAS) for more than thirty years. Patients from all over Bangladesh are sent to NINMAS for management of DTC after thyroidectomy.
Since a good number of patients with DTC are young and wish to have children, there remains concern that fertility may be impaired because of irradiation of ovaries and testicles. It is therefore needed to investigate the gonadal function in our population following RAI therapy for DTC. Till now no study has been conducted to assess prospectively the gonadal function in young patients with DTC following RAI therapy. This prospective longitudinal study is undertaken to assess the gonadal function of young adults with differentiated thyroid cancer following radioactive iodine ablation/therapy.
Young adults treated with radioactive iodine (I-131) for differentiated thyroid cancer suffer from gonadal dysfunction.
General Objective :
To assess gonadal function in young patients with differentiated thyroid cancer following RAI...
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