Page 833 - Textbook of Pathology, 6th Edition

Primary Hypoparathyroidism 817
Primary hypoparathyroidism is caused by disease of the
parathyroid glands. Most common causes of primary
hypoparathyroidism are: surgical procedures involving
thyroid, parathyroid, or radical neck dissection for cancer.
Other causes are uncommon and include idiopathic
hypoparathyroidism of autoimmune origin in children and
may occur as sporadic or familial cases. These cases are
generally associated with other autoimmune diseases.
CLINICAL FEATURES. The main biochemical dysfunctions
in primary hypoparathyroidism are hypocalcaemia,
hyperphosphataemia and hypocalciuria. The clinical
manifestations of these abnormalities are as under:
1. Increased neuromuscular irritability and tetany
2. Calcification of the lens and cataract formation
3. Abnormalities in cardiac conduction
4. Disorders of the CNS due to intracranial calcification
5. Abnormalities of the teeth.
Figure 27.21 Major clinical manifestations of hyperparathyroidism.
Pseudo-hypoparathyroidism
elsewhere in the body. Hypocalcaemia stimulates compen-
satory hyperplasia of the parathyroid glands and causes In pseudo-hypoparathyroidism, the tissues fail to respond
secondary hyperparathyroidism. to parathyroid hormone though parathyroid glands are
usually normal. It is a rare inherited condition with an
ETIOLOGY. Though any condition that causes hypo- autosomal dominant character. The patients are generally
calcaemia stimulates excessive secretion of parathyroid females and are characterised by signs and symptoms of
hormone, the important causes of secondary hyper- hypoparathyroidism and other clinical features like short CHAPTER 27
parathyroidism are as under: stature, short metacarpals and metatarsals, flat nose, round
1. Chronic renal insufficiency resulting in retention of face and multiple exostoses. Since renal tubules cannot
phosphate and impaired intestinal absorption of calcium. adequately respond to parathyroid hormone, there is hyper-
2. Vitamin D deficiency and consequent rickets and calciuria, hypocalcaemia and hyperphosphataemia.
osteomalacia may cause parathyroid hyperfunction.
3. Intestinal malabsorption syndromes causing deficiency of Pseudopseudo-hypoparathyroidism
calcium and vitamin D. Pseudopseudo-hypoparathyroidism is another rare familial
CLINICAL FEATURES. The main biochemical abnormality disorder in which all the clinical features of pseudo-
in secondary hyperparathyroidism is mild hypocalcaemia, hypoparathyroidism are present except that these patients The Endocrine System
in striking contrast to hypercalcaemia in primary have no hypocalcaemia or hyperphosphataemia and the
hyperparathyroidism. The patients with secondary tissues respond normally to parathyroid hormone.
hyperparathyroidism have signs and symptoms of the Pseudopseudo-hypoparathyroidism has been considered an
disease which caused it. Usually, secondary hyperparathy- incomplete form of pseudo-hypoparathyroidism.
roidism is a beneficial compensatory mechanism, but more
severe cases may be associated with renal osteodystrophy PARATHYROID TUMOURS
(i.e. features of varying degree of osteitis fibrosa, osteo-
malacia, osteoporosis and osteosclerosis in cases of chronic Parathyroid adenoma and carcinoma are the neoplasms
renal insufficiency) and soft tissue calcification (Fig. 27.21). found in parathyroid glands, the former being much more
common than the latter.
Tertiary Hyperparathyroidism
Tertiary hyperparathyroidism is a complication of secondary Parathyroid Adenoma
hyperparathyroidism in which the hyperfunction persists in The commonest tumour of the parathyroid glands is an
spite of removal of the cause of secondary hyperplasia. adenoma. It may occur at any age and in either sex but is
Possibly, a hyperplastic nodule in the parathyroid gland found more frequently in adult life. Most adenomas are first
develops which becomes partially autonomous and brought to attention because of excessive secretion of
continues to secrete large quantities of parathyroid hormone parathyroid hormone causing features of hyperparathy-
without regard to the needs of the body. roidism as described above.

HYPOPARATHYROIDISM MORPHOLOGIC FEATURES. Grossly, a parathyroid
adenoma is small (less than 5 cm diameter) encapsulated,
Deficiency or absence of parathyroid hormone secretion yellowish-brown, ovoid nodule and weighing up to 5 gm
causes hypoparathyroidism. Hypoparathyroidism is of 3 or more.
types—primary, pseudo- and pseudopseudo-hypoparathyroidism.