Background/Objectives: Epidemiological data on vitamin D status revealed that, despite various dosage and durations of supplementation, the effectiveness often fails to achieve optimal outcomes. The need for higher doses than previously recommended was suggested, but several modifying factors should be considered, including the level of deficiency, and BMI. The objectives of this post hoc evaluation are to characterize treatment effectiveness based on the applied dose, duration and BMI; and to assess the safety aspects associated with rapid repletion of vitamin D. Methods: Vitamin D deficient subjects selected in the post-hoc analysis: seventy patients included from a combined loading-maintenance supplementation (300,000 IU followed by 60,000 IU) protocol and 62 deficient subjects who received a low-dose maintenance (1000 IU/day) therapy. The risk of overload and the incidence of hypercalciuria and hypercalcemia resulting from loading or post-loading maintenance were investigated. Results: The moderate–fast-loading schedule of 60,000 IU per week for 5 weeks, effectively achieves the target in 25(OH)D levels over 30 ng/mL for all deficient subjects, regardless of their BMI. Slower loading with lower weekly doses confirms the safety of supplementation, but the effectiveness is dependent on the subjects’ BMI; overweight and obese patients require higher doses to reach the same vitamin D levels. No difference in safety parameters observed compared to low-dose therapies. Conclusions: The loading treatment involving a total dose of 300,000 IU administered over 5 or 10 weeks is effective for repletion, does not lead to 25(OH)D overload, and poses no additional risks of hypercalcemia or hypercalciuria. Furthermore, there are no safety concerns regarding changes in bone resorption markers. A combination of the loading treatment with a subsequent maintenance dose of 2000 IU daily is adequate to achieve the target vitamin D levels.

Background/Objectives: Vitamin D deficiency is common in women with polycystic ovary syndrome (PCOS) and may be associated with metabolic and endocrine disorders as well as ovulatory dysfunction. Vitamin D supplementation may improve ovarian dysfunction and follicular development by effecting gene expression. The aim of the present study was to investigate the effects of vitamin D supplementation in women with PCOS through a prospective, randomized, two-phase, parallel design, placebo-controlled trial. Methods: We assessed the impact on ovarian morphology, cycle length, and ovulatory dysfunction. Transvaginal ultrasonography (TVUS) examinations and clinical laboratory assessments were conducted at the baseline, and again after 12 and 24 weeks. The participants received vitamin D (30,000 IU/week) or a placebo (without concurrent metformin use) for 12 weeks, supplemented with calcium, followed by an additional 12 weeks of vitamin D treatment. Results: The treatment resulted in improvements in ovarian morphology and regularity of menstrual cycles in more than half of the patients. Additionally, vitamin D3 was associated with a significant increase in the ovulation rate. A statistically significant reduction in mean testosterone levels was observed in the subgroup of patients with an LH/FSH ratio greater than 2. Conclusions: Our results suggest that vitamin D3 treatment could function as either a standalone or an adjunctive therapy in the management of PCOS.