biology

Pseudohypoparathyroidism

Pseudohypoparathyroidism is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pseudohypoparathyroidism rather than just read about it. In short: Pseudohypoparathyroidism is a rare autosomal dominant genetic condition associated primarily with resistance to the parathyroid hormone. Those with the condition have a low serum calcium and high phosphate, but the parathyroid hormone level (PTH) is inappropriately high (due to the low level of calcium in the blood).

Key takeaways

Pseudohypoparathyroidism belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pseudohypoparathyroidism to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pseudohypoparathyroidism from memory before moving on to harder problems.

Reference excerpt

Pseudohypoparathyroidism is a rare autosomal dominant genetic condition associated primarily with resistance to the parathyroid hormone. Those with the condition have a low serum calcium and high phosphate, but the parathyroid hormone level (PTH) is inappropriately high (due to the low level of calcium in the blood). Its pathogenesis has been linked to dysfunctional G proteins (in particular, Gs alpha subunit). Pseudohypoparathyroidism is a very rare disorder, with estimated prevalence between 0.3 and 1.1 cases per 100,000 population depending on geographic location.

Types Types include:

Type 1a (OMIM 103580) Has a characteristic phenotypic appearance (Albright's hereditary osteodystrophy), including short fourth and fifth metacarpals and a rounded facies. It is most likely an autosomal dominant disorder. It is also associated with thyroid stimulating hormone resistance. Caused by GNAS1 mutation. Type 1b (OMIM 603233) Lacks the physical appearance of type 1a, but is biochemically similar. It is associated with a methylation defect in the A/B exon of GNAS1, caused by STX16 disruption. Type 2 (OMIM 203330) Also lacks the physical appearance of type 1a. Since the genetic defect in type 2 is further down the signalling pathway than in type 1, there is a normal cAMP response to PTH stimulation despite the inherent abnormality in calcium regulation. The specific gene is not identified. While biochemically similar, type 1 and 2 disease may be distinguished by the differing urinary excretion of cyclic AMP in response to exogenous PTH. Some sources also refer to a "type 1c" (OMIM 612462). The phenotype is the same as in type 1a, but red blood cells show normal Gs activity. As it is also caused by a GNAS mutation, it is not clear whether it should be considered an entity separate from Ia.

Presentation Patients may present with features of hypocalcaemia including carpo-pedal muscular spasms, cramping, tetany, and if the calcium deficit is severe, generalized seizures. IQ is typically mildly depressed or unaffected. Additional characteristics include short stature, obesity, developmental delay, and calcification of the basal ganglia in the deep white matter of the brain. Type 1a pseudohypoparathyroidism is clinically manifest by bone resorption with blunting of the fourth and fifth knuckles of the hand, most notable when the dorsum of the hand is viewed in closed fist position. This presentation is known as 'knuckle knuckle dimple dimple' sign (Archibald's sign). This is as opposed to Turner syndrome which is characterized by blunting of only the fourth knuckle, and Down syndrome, which is associated with a hypoplastic middle phalanx.

Related conditions The term pseudopseudohypoparathyroidism is used to describe a condition where the individual has the phenotypic appearance of pseudohypoparathyroidism type 1a, but is biochemically normal.

Diagnosis

Biochemical findings hypocalcemia hyperphosphatemia elevated parathyroid hormone (hyperparathyroidism) Suppressed calcitriol levels

Treatment Calcium and Calcitriol supplements, the latter with a larger dose than for treatment of hypoparathyroidism.

See also Hypoparathyroidism Pseudopseudohypoparathyroidism Hyperparathyroidism Rickets Hypervitaminosis D

References

Further reading Mantovani, G; Bastepe, M; Monk, D; de Sanctis, L; Thiele, S; Usardi, A; Ahmed, SF; Bufo, R; Choplin, T; De Filippo, G; Devernois, G; Eggermann, T; Elli, FM; Freson, K; García Ramirez, A; Germain-Lee, EL; Groussin, L; Hamdy, N; Hanna, P; Hiort, O; Jüppner, H; Kamenický, P; Knight, N; Kottler, ML; Le Norcy, E; Lecumberri, B; Levine, MA; Mäkitie, O; Martin, R; Martos-Moreno, GÁ; Minagawa, M; Murray, P; Pereda, A; Pignolo, R; Rejnmark, L; Rodado, R; Rothenbuhler, A; Saraff, V; Shoemaker, AH; Shore, EM; Silve, C; Turan, S; Woods, P; Zillikens, MC; Perez de Nanclares, G; Linglart, A (August 2018). "Diagnosis and management of pseudohypoparathyroidism and related disorders: first international Consensus Statement" (PDF). Nature Reviews. Endocrinology. 14 (8): 476–500. doi:10.1038/s41574-018-0042-0. PMC 6541219. PMID 29959430.

External links

Illustrations

Worked examples

Example 1 — a first encounter with Pseudohypoparathyroidism

Start with the simplest possible case. Write down what Pseudohypoparathyroidism claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pseudohypoparathyroidism before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pseudohypoparathyroidism ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pseudohypoparathyroidism

In research: Pseudohypoparathyroidism appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pseudohypoparathyroidism in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pseudohypoparathyroidism is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cell surface receptor deficiencies, Rare diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Pseudohypoparathyroidism outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Pseudohypoparathyroidism in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pseudohypoparathyroidism means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pseudohypoparathyroidism out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pseudohypoparathyroidism in simple terms?

Why does Pseudohypoparathyroidism matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pseudohypoparathyroidism?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pseudohypoparathyroidism.