ACTH, Calcitonin, HCG

Adrenocorticotropic hormone(ACTH)

Definition of ACTH

1. Adrenocorticotropic hormone (ACTH) is a peptide hormone secreted by the adenohypophysis.
2. It acts primarily on the adrenal cortex, stimulating its growth and synthesis of corticosteroids.
3. This hormone is also known as corticotropin, corticotrophin, adrenocorticotrophin, and adrenocorticotropin.

Pathophysiology of ACTH

1. ACTH hormone is synthesized by the anterior pituitary glands and stimulates the adrenal cortex.

2. This is a polypeptide hormone produced by the corticotropic cells of the anterior pituitary gland.
3. ACTH is a tropic hormone; it binds to the adrenal cortex cells and influences their activities.
4. ACTH in plasma is highest between 6 to 8 AM and lowest in the evening between 6 to 11 PM.
5. ACTH secretion is increased during stress.

2.  ACTH may be raised as primary or ectopic production.
3. Ectopic production from:
   1. Small cell carcinoma of the lung ( >200 ng/L).
   2. Pancreatic carcinoma.
   3. Breast.
   4. Stomach.
   5. Colon.
4. Benign conditions are:
   1. Chronic obstructive pulmonary disease.
   2. Mental depression.
   3. Obesity.
   4. Hypertension.
   5. Diabetes.
   6. Stress.
5. ACTH in a normal person does not exceed 50 pg/mL at its peak, and the basal level is near 5 pg/mL.
6. Raised ACTH level is seen in:
   1. In primary adrenal deficiency.
   2. In patients with Cushing’s syndrome.
   3. In patients with ectopic tumors e.g.
      1. Basophilic neoplasm of the anterior pituitary.
      2. Ectopic carcinoma of the lung.
7. Normal
   1. AM level = <80 pg/mL (<18 pmol/L).
   2. PM level = <50 pg/mL (<11 pmol/L).

Another reference

• 9 to 52 pg/mL (2 to 11 pmol/L)

Human Chorionic gonadotropin hormone (HCG)

1. This is also called Chorionic gonadotropin.
2. This is a glycoprotein secreted by the syncytiotrophoblastic cells of the placenta.
3. This consists of two subunits:
   1. α- HCG.
   2. β-HCG.
4. Elevated HCG level is seen in:
   1. Trophoblastic disease (level is usually >one million IU/L).
   2. Germ cell tumors and non-seminomatous tumors of the testis (there is a moderate increase).
   3. Reported in melanoma and carcinoma of the breast, GIT tumors, lung, and ovary.
5. The presence of HCG in seminoma indicates another component of choriocarcinoma.
6. Also raised in benign conditions like:
   1. Cirrhosis.
   2. Duodenal ulcer.
   3. Inflammatory bowel diseases.
   4. Pregnancy.
7. Normal HCG
   1. Male and nonpregnant females = <5 mIU/mL.

Calcitonin

Indications of calcitonin:

1. It is advised for the diagnosis of recurrence of medullary carcinoma.
2. It is also advised in metastases after the removal of the primary tumor.
3. Calcitonin is advised with basal value and after the surgery to see complete removal.

Calcitonin definition:

1. This is a polypeptide with 32 amino acids.
2. This is produced by the parafollicular C cells of the thyroid.
3. The serum half-life is 12 minutes.
4. In a normal person is <0.1 µg /L.
5. There is circadian variation in the calcitonin level, and the peak level is after lunchtime.

Mechanism of calcitonin:

1. Calcitonin acts directly on osteoclasts to decrease bone-resorbing activity and leads to a decrease in calcium levels.
2. This is produced in response to increased serum calcium levels.
3. Calcitonin is useful for the monitoring of disease after treatment.
4. It inhibits the release of calcium from the bone and lowers serum calcium.

Calcitonin is useful for diagnosing:

1. A basal fasting level of calcitonin may be increased in patients with medullary carcinoma of the thyroid, even in the absence of a palpable mass.
2. Medullary carcinoma of the thyroid. The level is >2000 pg/mL and is always associated with medullary carcinoma.
   1. A level of 500 to 2000 pg/mL generally indicates medullary carcinoma of thyroid, but also seen in renal failure or ectopic production of calcitonin.
   2. A level of 100 pg/mL to 500 pg/mL should be interpreted carefully, and do the provocative test; if the repeat test after 1 to 2 months is abnormal, then advise thyroidectomy.
3. Carcinoid tumor.
4. Lung cancers.
5. Breast cancer.
6. Kidney tumor.
7. Liver tumor.

Calcitonin levels also raised in nonmalignant conditions like:

1. Pulmonary disease.
2. Pancreatitis.
3. Hyperparathyroidism.
4. Paget’s disease of bone.
5. Pregnancy.
6. Pernicious anemia.

Normal (Source 2)

1. Basal (plasma)
   1. Male = ≤19 pg/mL  (≤19 ng/L)
   2. Female = ≤14 pg/mL  (≤14 ng/L)
2. Calcium infusion  (2.4 mg/kg)
   1. Male = ≤190 pg/mL  (≤190 ng/L)
   2. Femal =   ≤130 pg/mL  (≤130 ng/L)
3. Pentagastrin injection (0.5 µg/kg)
   1. Male = ≤110 pg/mL  (≤110 ng/L)
   2. Female = ≤30 pg/mL   (≤30 ng/L)

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