Management of Hypothyroidism in Prostate Cancer Treatment

Introduction to Orgovyx and Hypothyroidism

The American Urological Association (AUA) guidelines do not mention hypothyroidism as a side effect of Orgovyx (relugolix), a GnRH antagonist used for advanced prostate cancer 1
Orgovyx (relugolix) has common side effects including fatigue, hypertension, diarrhea, and hot flashes, but hypothyroidism is not listed as one of them 1

Immune checkpoint inhibitors can cause thyroid dysfunction in 6-20% of patients, according to the Journal for ImmunoTherapy of Cancer 2
Apalutamide (Erleada) causes hypothyroidism in approximately 8% of patients, as stated in the AUA guidelines 1
In the SPARTAN trial, hypothyroidism occurred in 8.1% of patients taking apalutamide versus 2.0% in the placebo group, with events generally identified early after starting treatment and manageable with medical therapy 1

Baseline thyroid function tests (TSH and free T4) should be obtained before starting treatment with medications that can cause hypothyroidism, as recommended by the Journal for ImmunoTherapy of Cancer and the Journal of Clinical Oncology 2, 3
Regular monitoring of thyroid function during treatment is recommended for patients taking medications that can cause hypothyroidism, according to the Journal for ImmunoTherapy of Cancer 2
For apalutamide specifically, particular attention should be paid to monitoring TSH in individuals with known hypothyroidism, as stated in the AUA guidelines 1
The American Thyroid Association recommends maintaining TSH within the reference range (0.45-4.5 mIU/L) for patients developing hypothyroidism, with monitoring of TSH levels every 6-8 weeks during dose titration 4