CHAPTER 17
Endocrine System
335
Blood
Blood
vessel
vessel
Blood
vessel
Septa
Blood
Blood
vessels
vessels
Blood
vessels
Capsule
Capsule
Capsule
Capsule
Capsule
A
Parathyroid Glands
Figure 17-9A.
Overview of the parathyroid glands.
H&E,
3
37
The four small
parathyroid glands
typically lie on the posterior
surface of the thyroid gland (Fig. 17-1) and are separated from
the thyroid gland by a connective tissue capsule. Connective tissue
septa with blood vessels divide each parathyroid gland into many
incomplete lobules. The parathyroid glands are derived from the
endoderm of pharyngeal pouch 3 (the inferior parathyroid glands)
and pouch 4 (the superior parathyroid glands). There are two
types of cells in the parathyroid glands:
chief cells
and
oxyphil
cells
(Fig. 17-9B). Adipocytes are commonly found in the parathy-
roid glands in older individuals.
Oxyphil cells
Oxyphil cells
Oxyphil cells
Capillary
Capillary
Capillary
Connective
Connective
tissue
tissue
septum
septum
Connective
tissue
septum
Blood
Blood
vessels
vessels
Blood
vessels
Oxyphil
Oxyphil
cells
cells
Oxyphil
cells
Chief
Chief
cells
cells
Chief
cells
Chief
Chief
cells
cells
Chief
cells
B
Figure 17-9B.
Chief cells and oxyphil cells of the parathyroid
glands.
H&E,
3
139; inset
3
296
The
chief cells
are smaller and more numerous than the
oxyphil cells
.
They are distributed throughout the glands and are the principal cells
in the parathyroid glands. Each
chief cell
has a large round nucleus
with a small amount of clear cytoplasm. These chief cells produce
PTH
, also called
parathormone
, which is secreted in response to
low blood calcium levels. PTH indirectly promotes osteoclast pro-
liferation and increases their activity of absorption of bone tissue to
increase blood calcium levels. The
oxyphil cells
are large cells with
acidophilic (pink) cytoplasm as shown here. Each cell has a small
nucleus and a large amount of cytoplasm containing numerous mito-
chondria. The oxyphil cells are often arranged in clusters; individual
cells can also be found scattered among the chief cells. The oxyphil
cells appear at puberty, and their numbers increase with age. Their
functions are unclear.
CLINICAL CORRELATION
Figure 17-9C.
Parathyroid Adenoma.
H&E,
3
96
Parathyroid adenomas
are benign
neoplasms
of the parathyroid
gland representing the most common cause of
primary
hyperpara-
thyroidism
, in which autonomous overproduction of parathyroid
hormone occurs. The increased parathyroid hormone results in
elevated blood calcium (
hypercalcemia
), which may cause constipa-
tion, kidney stones, neuropsychiatric issues, and bone diseases such
as
osteitis ± brosa cystica
. The majority of cases are asymptomatic,
discovered incidentally when hypercalcemia is detected on routine
blood tests. Most cases are sporadic, but some cases may be related
to inherited conditions like
multiple endocrine neoplasia
(MEN1
and MEN2). Parathyroid adenomas are usually solitary, whereas
parathyroid hyperplasia tends to affect all four glands. Grossly, these
adenomas are well circumscribed with a red-to-brown cut surface.
Histologically, an adenoma is enveloped with a capsule, is usually
composed of
monomorphic chief cells
, and tends to compress the
surrounding normal parathyroid tissue. De± nitive treatment is surgi-
cal removal of the parathyroid gland containing the adenoma.
C
Adenoma
composed
of chief cells
Normal
parathyroid
gland with
adipose tissue
Adipocytes
previous page 350 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online next page 352 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online Home Toggle text on/off