Parathyroid function in rats treated with growth hormone. A morphometric study

Clinical MEN-1 Among a Large Cohort of Patients With Acromegaly

CONTEXT

Clinical multiple endocrine neoplasia type 1 (MEN-1) is diagnosed by the presence of at least 2 MEN-1-associated tumors. Many patients with acromegaly and clinical MEN-1 yield negative testing for MEN1 mutations. While cases of acromegaly and primary hyperparathyroidism (PHP) with negative genetic testing have been reported, its prevalence among patients with acromegaly is undetermined, and the clinical presentation has not been well characterized.

OBJECTIVES

The main goals of this study are: (1) To determine the prevalence of clinical MEN-1 with PHP in patients with acromegaly and characterize their clinical features; and (2) to evaluate the genetic basis for the coexistence of acromegaly and PHP.

DESIGN

Retrospective record review and genetic analysis.

SETTING

Clinical Research Centers.

PARTICIPANTS

414 patients with acromegaly.

INTERVENTIONS

Clinical evaluation and DNA sequencing for MEN1, CDKN1A, CDKN1B, CDKN2B, CDKN2C, and AIP genes.

MAIN OUTCOME MEASUREMENTS

Clinical and genetic analysis.

RESULTS

Among patients with acromegaly, clinical MEN-1, as defined by the presence of at least one other MEN-1-associated tumor, was present in 6.6%. PHP occurred in 6.1%; more than half had parathyroid hyperplasia. DNA sequencing was unrevealing for genetic mutations, except for 1 case of a CDC73 mutation. Acromegaly was diagnosed at an older age with a higher prevalence of malignancies (specifically breast and thyroid) in patients with coexisting PHP than those with isolated acromegaly.

CONCLUSIONS

A distinct phenotype is described in patients with clinical MEN-1 and negative genetic testing for mutations previously associated with this syndrome. Further studies are needed to identify other genes that may explain the association between PHP and acromegaly.

The parathyroid gland in metal rickets. A stereological study

Rickets can be induced by oral administration of metals. A depressive effect exerted by metal ions on the parathyroid gland has previously been suggested to be a pathogenetic factor in strontium-induced rickets. In the present investigation, rickets was induced in young rats by oral administration of strontium and manganese, respectively. The parathyroids were fixed by perfusion and the total volume of the parathyroid glands was determined by serial sectioning. Conventional stereological techniques were applied on the ultrastructural level and the densities obtained could be related to the total mass of parathyroid tissue. In both rachitic groups the volume of the parathyroid glands as well as the absolute amounts of all cellular components studied, were reduced. All these changes were, however, correlated to the decreased body weight of the experimental animals. This is well in line with the finding of unaltered serum concentrations of calcium and immunoreactive parathyroid hormone. Therefore, it is concluded that the parathyroids do not play an important role in the pathogenesis of metal rickets.

Quantitative morphological assessment of parathyroid activity in response to variations in calcium concentration in vitro

Isolated parathyroid glands from gerbils incubated at low (0.5 mM), normal (1.25 mM) or high (3 mM) calcium concentration for 1 or 6 h were studied with regard to the following stereological parameters: the volume densities of the nucleus, mitochondria, endoplasmic reticulum, Golgi zone, lipid bodies, lysosomes, secretory granules and storage granules, and the surface densities of the cell membrane and endoplasmic reticulum. In glands incubated for 1 h no significant differences were seen between the experimental groups in any of the parameters investigated, however, the volume density of the Golgi zone and the surface density of the cell membrane were significantly increased in glands incubated for 6 h at low calcium concentration, compared with those incubated at high calcium concentration. The enlargement of the Golgi zone in stimulated glands was also evident when the two glands from the same animal incubated at different calcium concentrations were compared. The data suggest that the early response of parathyroid glands to altered concentration of extracellular calcium includes functional activities associated with the Golgi zone.

Pituitary adenoma, primary parathyroid hyperplasia and papillary (non-medullary) thyroid carcinoma. A case of multiple endocrine neoplasia (MEN)

An acidophilic pituitary adenoma associated with primary nodular parathyroid hyperplasia and a small papillary thyroid carcinoma was discovered at the autopsy of a 44 year old female acromegalic. The thyroid carcinoma showed evidence of lymphatic spread. Several etiopathogenetic mechanisms for the non-medullary thyroid carcinomata associated with Multiple Endocrine Neoplasia (MEN) have been postulated, since the follicular epithelium of the thyroid does not belong to the neural ectoderm derivates unlike the C-cells of the thyroid, the adenohypophysis and probably the parathyroid glands. Apart from genetic influence, or coincidence, one has to rule out carcinogenic exposure or hormonal influence. Clinically speaking, one should always consider whether malignant thyroid disease coexists with hyperplastic or neoplastic parathyroid tissue.