According to Gram Research analysis, severe vitamin D deficiency can hide the typical signs of an overactive parathyroid gland, causing it to present with low blood calcium instead of the expected high calcium. A case report of a 30-year-old woman with a giant 3.5-gram parathyroid tumor demonstrates this dangerous masking effect: her parathyroid hormone was markedly elevated, but her calcium remained low due to severe vitamin D deficiency. Only after vitamin D supplementation normalized her calcium did the persistently high parathyroid hormone reveal the true diagnosis of primary hyperparathyroidism, leading to successful surgical removal of the tumor.
A 30-year-old woman experienced bone pain and fatigue for nine months, but doctors initially missed her diagnosis because severe vitamin D deficiency was masking her real problem: a giant parathyroid tumor. Normally, overactive parathyroid glands cause high calcium levels in the blood, but her vitamin D deficiency kept her calcium dangerously low instead. After receiving vitamin D and calcium supplements, her calcium normalized but her parathyroid hormone remained abnormally high—the key clue that revealed a 3.5-gram parathyroid adenoma. A specialized imaging scan found the tumor that ultrasound had missed, and surgery successfully removed it. This case shows how vitamin D deficiency can hide serious parathyroid disease and delay diagnosis.
Key Statistics
A 2026 case report documented a giant parathyroid adenoma weighing 3.5 grams that presented with low blood calcium instead of the typical high calcium, because severe vitamin D deficiency masked the condition in a 30-year-old woman.
In this case report, two ultrasound examinations failed to detect the parathyroid tumor, but 99mTc-sestamibi scintigraphy successfully identified the hyperfunctioning gland, highlighting the importance of functional imaging when anatomic studies are inconclusive.
The patient’s parathyroid hormone remained inappropriately elevated even after calcium supplementation normalized her blood calcium levels, which was the critical diagnostic clue that revealed autonomous parathyroid disease rather than secondary hyperparathyroidism from vitamin D deficiency alone.
The Quick Take
- What they studied: How severe vitamin D deficiency can hide the typical signs of an overactive parathyroid gland, making diagnosis difficult
- Who participated: One 30-year-old woman from Syria who presented with nine months of bone pain, fatigue, and finger tingling
- Key finding: A giant parathyroid tumor (3.5 grams) presented with low blood calcium instead of the expected high calcium, because severe vitamin D deficiency masked the condition
- What it means for you: If you have bone pain, fatigue, and low vitamin D, doctors should check your parathyroid hormone levels even if your calcium is low. This case reminds healthcare providers to look deeper when symptoms don’t match typical patterns
The Research Details
This is a case report describing the medical experience of a single patient. A 30-year-old woman came to the hospital with nine months of progressive fatigue, bone pain throughout her body, tingling in her fingertips, and neck discomfort. Blood tests showed she had severe vitamin D deficiency, low calcium levels, and very high parathyroid hormone levels—an unusual combination that initially confused doctors because it looked like secondary hyperparathyroidism (when the parathyroid gland overworks because of vitamin D deficiency) rather than primary hyperparathyroidism (when the parathyroid gland itself is diseased).
The doctors started treating her with calcium and vitamin D supplements. Her calcium levels improved, but her parathyroid hormone stayed dangerously high. This abnormal pattern was the clue that revealed she had an autonomous parathyroid tumor—a gland that was malfunctioning on its own, not just reacting to low vitamin D. Two ultrasound scans couldn’t find the tumor, but a specialized nuclear medicine scan called 99mTc-sestamibi scintigraphy detected a hyperactive parathyroid gland on the left side of her neck.
Surgeons performed focused parathyroidectomy (removal of just the diseased parathyroid gland) and removed a 3.5-gram adenoma—unusually large for a parathyroid tumor. Pathology confirmed it was benign. After surgery, her calcium remained stable and her parathyroid hormone normalized. She recovered without complications and had normal blood work at follow-up.
This case is important because it shows how vitamin D deficiency can completely change how a parathyroid disease presents, leading doctors down the wrong diagnostic path. Understanding this atypical presentation helps physicians recognize when to use additional imaging tests and when to suspect primary hyperparathyroidism even when calcium levels are low.
This is a single case report, which is the lowest level of scientific evidence. Case reports describe one person’s experience and cannot prove cause-and-effect or be generalized to larger populations. However, case reports are valuable for documenting unusual presentations of disease and teaching doctors about diagnostic challenges. The detailed clinical information and successful surgical outcome make this case medically instructive.
What the Results Show
The patient presented with an unusual biochemical pattern: markedly elevated parathyroid hormone (indicating parathyroid overactivity) combined with low blood calcium and severe vitamin D deficiency. This combination initially suggested secondary hyperparathyroidism—where the parathyroid gland overworks to compensate for vitamin D deficiency—rather than primary hyperparathyroidism, where the gland itself is diseased.
When vitamin D and calcium supplementation normalized her calcium levels but parathyroid hormone remained inappropriately elevated, this revealed the true diagnosis: an autonomous parathyroid tumor. The patient’s parathyroid hormone should have decreased once calcium was restored, but it didn’t—proving the gland was malfunctioning independently.
Imaging studies showed the limitations of standard ultrasound: two ultrasound examinations failed to identify the tumor. However, 99mTc-sestamibi scintigraphy (a nuclear medicine scan that detects overactive parathyroid tissue) successfully localized a hyperfunctioning left inferior parathyroid gland. Surgery revealed a 3.5-gram adenoma—at the threshold for classification as a ‘giant’ parathyroid adenoma, which is rare.
Postoperatively, the patient achieved complete biochemical cure with normalized calcium and appropriately suppressed parathyroid hormone levels. She experienced no complications such as hungry bone syndrome (a condition where calcium drops dangerously after parathyroid surgery) and was discharged the same day with an uneventful recovery.
The patient’s initial symptoms—progressive fatigue, generalized bone pain, intermittent paresthesia (tingling), and cervical discomfort—all resolved after surgery. Physical examination had been unremarkable with no palpable neck mass, demonstrating that large parathyroid tumors can be located deep in the neck where they’re not detectable by touch. Histopathological examination confirmed the adenoma was benign without capsular or vascular invasion, indicating no evidence of malignancy.
Giant parathyroid adenomas (≥3.5 grams) are rare, accounting for only a small percentage of primary hyperparathyroidism cases. Most giant adenomas present with severe hypercalcemia (high blood calcium) due to excessive parathyroid hormone secretion. This case is unusual because the giant adenoma presented with hypocalcemia (low blood calcium) due to concurrent severe vitamin D deficiency. The literature emphasizes that vitamin D deficiency can mask the biochemical features of primary hyperparathyroidism, but documented cases of giant adenomas with this atypical presentation are uncommon. This case adds to the medical literature by illustrating how diagnostic delays can occur when clinical presentation doesn’t match expected patterns.
This is a single case report involving one patient, so findings cannot be generalized to other patients or populations. Case reports describe what happened in one person’s experience but cannot prove that vitamin D deficiency always masks parathyroid adenomas or that this presentation is common. The patient’s age (30 years old) and geographic origin (Syria, where vitamin D deficiency may be more prevalent) may limit applicability to other populations. Additionally, this case cannot determine how often this atypical presentation occurs or identify which patients are at highest risk. Larger studies would be needed to understand the frequency and characteristics of parathyroid adenomas presenting with hypocalcemia.
The Bottom Line
Healthcare providers should consider measuring parathyroid hormone levels in patients with bone pain, fatigue, and vitamin D deficiency, even if blood calcium is low. When calcium supplementation and vitamin D repletion fail to suppress parathyroid hormone to normal levels, this suggests primary hyperparathyroidism rather than secondary hyperparathyroidism. If ultrasound is inconclusive, functional imaging such as 99mTc-sestamibi scintigraphy should be pursued. For patients with suspected parathyroid disease, focused parathyroidectomy by experienced surgeons offers excellent outcomes with same-day discharge and rapid recovery. (Confidence level: Based on single case report; recommendations reflect standard clinical practice)
This case is most relevant to physicians, especially primary care doctors, endocrinologists, and surgeons who evaluate patients with bone pain, fatigue, and vitamin D deficiency. Patients with unexplained bone symptoms and low vitamin D should be aware that their parathyroid gland should be evaluated. This case is less directly applicable to patients without vitamin D deficiency or those with typical presentations of hyperparathyroidism.
In this case, symptoms developed over nine months before diagnosis. After vitamin D and calcium supplementation, biochemical abnormalities became apparent within a timeframe that allowed surgical planning. Post-operative recovery was rapid, with same-day discharge and complete symptom resolution. Realistic expectations: diagnosis may take weeks to months if atypical presentations delay recognition; surgical recovery typically occurs within days to weeks.
Frequently Asked Questions
Can vitamin D deficiency hide parathyroid disease?
Yes. Severe vitamin D deficiency can lower blood calcium levels, masking the high calcium typically seen with overactive parathyroid glands. This atypical presentation can delay diagnosis, as demonstrated in a 2026 case of a giant parathyroid adenoma that presented with low calcium instead of high calcium.
What imaging test is best for finding parathyroid tumors?
When ultrasound is inconclusive, 99mTc-sestamibi scintigraphy (a nuclear medicine scan) is more effective at detecting overactive parathyroid tissue. In this case report, ultrasound missed the 3.5-gram adenoma, but sestamibi scintigraphy successfully located it.
What symptoms suggest parathyroid problems?
Bone pain, fatigue, tingling in fingers, and neck discomfort can indicate parathyroid disease. If these symptoms occur alongside vitamin D deficiency, doctors should check parathyroid hormone levels even if blood calcium is low, as this case demonstrates.
How quickly do parathyroid surgery patients recover?
Recovery can be rapid. In this case report, the patient was discharged the same day after focused parathyroidectomy and had an uneventful recovery with normal biochemical findings at follow-up, experiencing complete symptom resolution.
How common are giant parathyroid adenomas?
Giant parathyroid adenomas (weighing at least 3.5 grams) are rare, accounting for only a small percentage of primary hyperparathyroidism cases. Most present with high blood calcium, making this case’s presentation with low calcium particularly unusual.
Want to Apply This Research?
- Track parathyroid hormone levels quarterly if you have vitamin D deficiency, bone pain, or fatigue. Record calcium levels, vitamin D levels, and symptom severity (fatigue, bone pain, tingling) on a 1-10 scale weekly to identify patterns and share with your healthcare provider
- If diagnosed with vitamin D deficiency, consistently take prescribed vitamin D and calcium supplements as directed, and schedule follow-up blood work to confirm levels are normalizing. If parathyroid hormone remains elevated despite vitamin D repletion, request referral to an endocrinologist for further evaluation
- Maintain a symptom diary documenting fatigue, bone pain location and intensity, and any tingling sensations. Log all supplement intake and blood test results. Share this data with your healthcare provider at each visit to help identify whether symptoms improve with treatment or persist despite normalization of vitamin D levels
This article describes a single case report and represents the lowest level of medical evidence. Case reports document one person’s experience and cannot be generalized to other patients or populations. This information is educational and should not replace professional medical advice. If you experience bone pain, fatigue, or symptoms suggestive of parathyroid disease, consult with a qualified healthcare provider for proper evaluation, diagnosis, and treatment. Do not make medical decisions based solely on this case report. Always discuss your individual health concerns with your doctor, who can assess your specific situation and recommend appropriate testing and management.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.