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HYPERPARATHYROIDISM

The parathyroid glands are located alongside the thyroid gland and produce parathyroid hormone which regulates calcium metabolism.  Hyperparathyroidism is the condition where an excessive amount of parathyroid hormone is produced resulting in low serum levels of calcium. The following study indicates that hyperparathyroidism commonly coexists with hyperthyroidism (77% in this study), at least in cats.

 

J Small Anim Pract 1996 Dec;37(12):575-82

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Study of calcium homeostasis in feline hyperthyroidism.

Barber PJ, Elliott J

Department of Veterinary Basic Sciences, Royal Veterinary College, University of London.

Thirty cats with untreated hyperthyroidism were blood sampled and their calcium homeostatic mechanisms and renal function assessed. The results were compared with those obtained from 38 age-matched control cats. The hyperthyroid group of cats were found to have significantly lower blood ionised calcium and plasma creatinine concentrations and significantly higher plasma phosphate and parathyroid hormone concentrations. Hyperparathyroidism occurred in 77 per cent of hyperthyroid cats, with parathyroid hormone concentrations reaching up to 19 times the upper limit of the normal range. The aetiology, significance and reversibility of hyperparathyroidism in feline hyperthyroidism remains to be established but could have important implications for both bone strength and renal function.

Parathyroid Hormone Therapy Reverses Idiopathic Osteoporosis in Men

WESTPORT, CT (Reuters Health) Oct 5 - In men with idiopathic osteoporosis, treatment with parathyroid hormone substantially increases bone density by enhancing bone turnover, according to a report in the September Journal of Clinical Endocrinology and Metabolism.

Four out of ten men diagnosed with osteoporosis will have no obvious etiology for their disease except low bone turnover, Dr. Etah Kurland from Columbia University College of Physicians and Surgeons in New York and colleagues explain. The current antiresorptive treatments offer little benefit for these patients.

Recognizing the bone turnover-increasing properties of parathyroid hormone, the researchers conducted a randomized, controlled trial in which ten young and middle-aged patients with idiopathic osteoporosis received daily subcutaneous doses of PTH-(1-34), a fragment of parathyroid hormone, for 18 months, and 13 patients received placebo injections of vehicle.

PTH treatment significantly increased lumbar spine bone density (4.8% at 6 months and 13.5% at 18 months), the authors report, and gradually increased femoral neck bone density (2.9% at 18 months). Bone density did not change in control patients.

All markers of bone turnover increased in the men treated with PTH, the researchers note. Serum osteocalcin, a marker of bone formation, increased by 230% at 1 year, whereas urinary pyridinoline excretion, a marker of bone resorption, increased by 131% after 9 months.

Hypercalcemia developed in 2 of 10 PTH-treated patients but resolved after the PTH dose was lowered, the investigators fund. Apart from redness at the injection site, there were no other treatment-related adverse effects.

"PTH-(1-34) shows great potential as an effective anabolic agent for the treatment of idiopathic osteoporosis in men and may serve as a valuable addition to the limited array of drugs currently available to treat this disorder," the authors conclude.

J Clin Endocrinol Metab 2000;85:3069-3076.