ABSTRACT
            Background and Objectives: Vitamin D is an essential secosteroid that plays a crucial role in the homeostasis of a few mineral elements, particularly calcium. Since vitamin D deficiency and thyroid diseases are two important global health problems, we aimed to investigate a possible relationship of vitamin D and calcium levels with hypothyroidism in an Iranian population.
            Methods: This case-control study was conducted on 175 subjects with hypothyroidism (75 males and 100 females) and 175 euthyroid controls (85 males and 90 females) who were referred to a laboratory in Gorgan, Iran. Serum levels of 25-hydroxyvitamin D, calcium, thyroid-stimulating hormone (TSH), free triiodothyronine (free T3) and thyroxine (total T4) were measured in all participants.
            Results: Vitamin D and calcium were significantly lower in patients with hypothyroidism (P<0.0001). Free T3 and calcium levels differed significantly among hypothyroid patients based on their vitamin D status (P<0.0001), but vitamin D levels were within sufficient range in all groups. Moreover, there was a positive correlation between free T3 with vitamin D (r= 0.337, P<0.0001) and calcium (r= 0.361, P<0.0001) levels.
            Conclusions: Our results suggest that there may be a relationship between decreased vitamin D levels and thyroid function parameters.
            Keywords: Vitamin D Deficiency, Hypocalcemia, Hypothyroidism, Thyrotropin, Thyroxine.

Background: Hyperbilirubinemia is the most common clinical abnormality in newborns during the first week of life. Phototherapy is the standard treatment but may cause complications, including hypocalcemia, a lesser-known yet significant adverse effect. This study investigated the impact of phototherapy on serum calcium levels in neonates with hyperbilirubinemia.
Methods: This observational study was conducted in the NICU of BYL and T.N. Medical College, Mumbai, over 12 months after ethical approval. We included 100 neonates (> 34 weeks gestational age) with hyperbilirubinemia receiving phototherapy. Serum calcium levels were measured before and after phototherapy, and neonates were monitored for clinical hypocalcemia. Data were recorded in a pre-formatted proforma and analyzed using SPSS version 27 (p <0.05 was considered statistically significant).
Results: The mean age of neonates was 3±1.2 days, the mean gestational age was 37±1.2 weeks, and the mean jaundice duration was 2.8±1.10 days. Median serum calcium levels decreased significantly from 8.6 mg/dL (8.49-8.61) pre-phototherapy to 7.35 mg/dL (7.33-7.50) post-phototherapy (p <0.001). Hypocalcemia (serum calcium ≤7 mg/dL) occurred in 16% of neonates, with 60% exhibiting mild symptoms like jitteriness or irritability.
Conclusion: Phototherapy significantly reduces serum calcium levels in jaundiced neonates, with a notable incidence of hypocalcemia. Clinicians should monitor calcium levels and watch for symptoms during phototherapy to prevent complications. Further studies are needed to establish preventive strategies.