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The purpose of the study was to assess the endocrine effects of vandetanib, a multikinase inhibitor targeting RET, vascular endothelial growth factor receptor, and epidermal growth factor receptor, in 39 patients with progressive thyroid cancer included in two randomized placebo-controlled trials using vandetanib 300 mg/d.Endocrine samplings were performed at baseline and then every 6 months. We compared differences in endocrine parameters between baseline and on vandetanib therapy or placebo.During vandetanib treatment, several changes were observed. 1) Calcium (P = 0.0004) and vitamin D (P = 0.001) mean replacement doses were increased; calcium level remained unchanged, but serum 25(OH) vitamin D level decreased (P = 0.001); and serum PTH (P = 0.01) and 1,25(OH)(2) vitamin D (P = 0.01) levels increased, suggesting a decreased intestinal absorption of vitamin D or lack of sun exposure as a result of photosensitization. 2) l-T(4) doses were increased (P0.0001) to maintain serum TSH within the normal range. 3) In male patients, total testosterone (P = 0.048), bioavailable testosterone (P = 0.03), and SHBG (P = 0.02) levels increased. Serum inhibin B decreased (P = 0.02) and stimulated FSH increased (P = 0.006), suggesting a Sertoli cells insufficiency. 4) Cortisol level increased (P = 0.007) as well as ACTH level (P = 0.03) and cortisol-binding globulin (P = 0.02), but free urinary cortisol levels remained in the normal range. None of these changes were observed in patients randomized to the placebo arm.In patients with locally advanced or metastatic thyroid cancer, the tyrosine kinase inhibitor vandetanib has several endocrine effects. Thyroid hormone, calcium, and vitamin D analog requirements increased, but consequences of the biological alterations on phosphocalcic metabolism and gonadotrope and adrenal functions are unknown.

Many drugs can induce hyperandrogenic symptoms, such as hirsutism, acne, seborrheic dermatitis, male-pattern baldness, menstrual irregularities, clitoral hypertrophy, or deepening of voice. Anabolic-androgenic steroids, synthetic progestins, and antiepileptics are the most frequently implicated drugs in hyperandrogenism. The mechanisms of androgen excess are various: (1) intrinsic androgenic activity of the drug, (2) interaction with sex hormone-binding globulin, or (3) functional alterations of the hypothalamic-pituitary-ovary axis. Nevertheless, the physiology of these drugs remains generally unclear. Such is the case for valproate, which seems to induce a form of polycystic ovary syndrome (PCOS) by increasing ovarian androgen synthesis. It should be remembered that it is always necessary to rule out other causes of androgen excess, especially an ovarian or adrenal tumor or PCOS, before attributing the symptom(s) to a drug.